OPINION OF THE COURT

VAN DUSEN, Senior Circuit Judge.

Plaintiff, American Bearing Company, Inc. ("American"), appeals from the district court's order of May 26, 1982, denying the motion of defendant, Litton Industrial Products, Inc. ("Litton"), for a judgment notwithstanding the verdict but granting a new trial. Plaintiff commenced this action for product defamation, monopolization, and attempted monopolization, predicating its claims on the dissemination of an allegedly false Litton memorandum that evaluated an American product. A jury found Litton liable for monopolization and attempted monopolization in violation of section 2 of the Sherman Act, 15 U.S.C. § 2 (1976), but not for product defamation. The jury awarded American $958,691., which amount the court trebled. See the Clayton Act, 15 U.S.C. § 15 (1976 Supp. IV 1982). Ruling on Litton's post-trial motions, the court, pursuant to Fed.R.Civ.P. 50(b), set aside the jury verdict and ordered a new trial. See American Bearing Co. v. Litton Industries, Inc., 540 F. Supp. 1163 (E.D.Pa. 1982). At the end of the second trial, the district court granted defendant's motion for a directed verdict at the close of plaintiff's case on liability and entered judgment for defendant on March 9, 1983 (5794a). We affirm.

I.

American, a New Jersey corporation, manufactures and sells, among other things, bearings for use in construction and industrial applications. Litton, a Delaware corporation, manufactures a wide variety of industrial products and equipment; its Merriman division manufactures and sells bearings for use in construction and industrial applications. Both companies manufacture a slide bearing used in electrostatic precipitators and baghouses, types of industrial air pollution control equipment.

Slide bearings are engineered items that are specified and fabricated on a job-by-job basis. They are manufactured in a variety of sizes from a variety of materials, including bronze, meehanite, steel, and Teflon, to meet the builders' specifications. Builders typically specify the parameters at which the bearings will be required to operate and manufacturers of bearings submit bids for those of their bearings that will meet the specifications. Specifications are normally stated in terms of temperature, pressure, and coefficients of friction. Slide bearings are positioned at the structural support points of precipitators and baghouses to permit the structural supports to move freely in response to the expansion and contraction of steel columns.

Until 1975, American manufactured a slide bearing called the "Tetra-slide" bearing; the Tetra-slide bearing, however, could not meet the design specifications for precipitators and baghouses. At this time, Litton held patents on two structural support bearings, "Lubrite F" and "Lubritemp," which were used extensively in precipitators and baghouses. American, realizing the potential profit in designing bearings for precipitators and baghouses, attempted to design a bearing that would meet the specifications of builders but would not infringe Litton's patents (247a-52a, 414a-15a). American developed such a bearing, designated it the "Hi-Load" bearing, and eventually patented it. American marketed its bearing as one appropriate for use in high temperature precipitator and baghouse structural support applications. As part of its marketing strategy, American distributed sales samples, measuring two inches by two inches, to potential purchasers in the air pollution control industry.

Litton learned in early 1976 that one of its slide bearing customers, the Carborundum Company ("Carborundum"), was considering the purchase of American's "Hi-Load" bearing (714-15a, 723-25a). The specifications for the Carborundum job required that the bearing be able to withstand 3000 pounds of pressure per square inch ("p.s.i.") and 400° F. temperature. Doubting that American's Hi-Load bearing was capable of meeting the specifications, Litton tested one of American's samples. After conducting the test, Litton drafted a memorandum that concluded: "Therefore it is our opinion that this bearing cannot function at the specified load and temperature conditions" (2438a). During the next four years, Litton furnished copies of the memorandum to its salesmen without restricting its distribution. Litton, in fact, disseminated the memorandum to purchasing agents and engineers at several pollution equipment manufacturing companies (442-47a).

Finding itself unable to sell the "Hi-Load" bearing, American initiated this suit on June 15, 1978, alleging that the test memorandum was false and that Litton's publication of the memorandum constituted product defamation. Moreover, American asserted that Litton attempted to monopolize, and did monopolize, the market for slide bearings between 1976 and June 15, 1978, in violation of section 2 of the Sherman Act.

II.

Trial commenced on May 19, 1981. American sought to establish its claims by presenting the testimony of four expert witnesses. American's first expert, J. Albert Hudson, explained generally the structure and purposes of precipitators and baghouses. One of Hudson's most important contributions was his testimony that there is an average cost ratio of 0.003 or 0.3% between the cost of slide bearings installed in precipitators and baghouses and the costs of the precipitators and baghouses themselves. American's second expert, Robert W. McIlvaine, testified to national sales statistics for precipitators and baghouses that utilize an inlet gas temperature of 250° or higher. He estimated that the aggregate dollar amount of precipitator and baghouse sales for the years 1976 to 1983 was $3,180,900,000. (796a, 2465a).

Dr. Gary W. Bowman, an Associate Professor of Economics at Temple University, was American's final expert witness. He presented economic testimony to the jury, defined product and geographic markets, estimated the market shares of American and Litton, and estimated the damages American suffered from 1976 to 1983. Dr. Bowman defined "thermal" bearings as bearings which operate with a 3% coefficient of friction while exposed to temperature of 400° F. and pressure of 3000 p.s.i. (1263a, 1335a). He gave his opinion that a separate market exists for thermal bearings for use in the support structures of baghouses and precipitators and opined that the market was nationwide. Dr. Bowman was unable to ascertain directly American's damages. Instead, he attempted to calculate damages indirectly by utilizing the sales statistics presented by McIlvaine and the cost ratio presented by Hudson. Dr. Bowman determined the size of the total market for slide bearings simply by multiplying the sales statistics (2465a) by the cost ratio of 0.003 (2719a, 1266-67a). The multiplication process led Dr. Bowman to conclude that from 1976 to 1983 the aggregate sales for the nationwide market for slide bearings capable of operating at 3000 p.s.i., 400° F., with a 3% coefficient of friction, totaled $9,542,700. (2719a). Dr. Bowman offered an opinion as to the market share American would have captured absent the circulation of Litton's test report and estimated the amount of profits American lost as a result of Litton's test report. He concluded that American lost $1,611,279. as a result of Litton's memorandum and related activities (2719a).

After three weeks of testimony, the jury returned a verdict in answer to special interrogatories. The jury found that Litton was not responsible for product defamation, but was liable both for monopolization and attempted monopolization in violation of section 2 of the Sherman Act, 15 U.S.C. § 2 (1976); it assessed damages in the amount of $958,691. The district court, pursuant to section 4 of the Clayton Act, 15 U.S.C. § 15 (1976 Supp. IV 1982), trebled the jury's award and entered judgment in favor of American in the amount of $2,876,073.

Litton then filed a motion under Fed.R.Civ.P. 50(b) for judgment notwithstanding the verdict or, alternatively, for a new trial. In ruling on this motion, the district court held that it should have excluded Dr. Bowman's testimony under Fed.R.Evid. 403 and 703. The basis of this holding was that Dr. Bowman based his testimony on speculation and unsupported assumptions, and that Dr. Bowman calculated damages based on figures which included bearings outside the market which he had defined for purposes of proving monopolization. The district court then ordered a new trial. The court declined to decide whether it would have been justified in granting a judgment n.o.v., deciding instead that a new trial was needed in any event to avoid a miscarriage of justice.

Pursuant to the court's new trial order, retrial commenced on February 28, 1983. At that trial, the district court made two evidentiary rulings that were adverse to plaintiff's case. Faced with the adverse evidentiary rulings, American presented an offer of proof of the testimony of one of its experts, withdrew the witness, moved its exhibits into evidence, and rested without proving a prima facie case. Defendants moved for a directed verdict, and the district court granted the motion. In its brief filed in this court, plaintiff challenged these two allegedly erroneous evidentiary rulings. At oral argument in this court, however, plaintiff waived its reliance on these allegedly erroneous rulings and limited its appeal to the propriety of the district court's decision to grant a new trial (Transcript of Oral Argument filed November 30, 1983, at 2). Our review, therefore, is limited to reviewing the propriety of the new trial order. If we affirm, the directed verdict plaintiff suffered at retrial will be unaffected. If, however, we should conclude that the district court abused its discretion by granting a new trial, we would remand for reinstatement of the jury verdict.

Because of the deficiencies in American's proof on the subjects of the relevant product market and causation in fact, we hold that the district court properly granted a new trial to prevent injustice and because the verdict was against the weight of the evidence. Since American has waived its objections to any errors in the second trial, we affirm the judgment for Litton.

III.

To determine whether the district court properly granted a new trial under Fed.R.Civ.P. 50(b), we first must determine the appropriate legal standard for granting a new trial under that rule. Fed.R.Civ.P. 50(b) provides, in relevant part:

"[A motion for] a new trial may be prayed for in the alternative. If a verdict was returned the court may allow the judgment to stand or may reopen the judgment and either order a new trial or direct the entry of judgment as if the requested verdict had been directed." (Emphasis added.)

In this case, Litton made an alternative motion for a new trial. In such a circumstance, "the motion is tested by the same standards that would apply if the motion were independently made under rule 59." 9 C. Wright A. Miller, Federal Practice Procedure § 2539, at 608 (1971). A district court, therefore, may grant a new trial if required to prevent injustice or to correct a verdict that was against the weight of the evidence. Thomas v. E.J. Korvette, Inc., 476 F.2d 471, 474-75 (3d Cir. 1974); 6A J. Moore, Moore's Federal Practice ¶ 59.08[5], at 59-140, 59-152 (2d ed. 1982). "The authority to grant a new trial, moreover, is confided almost entirely to the exercise of discretion on the part of the trial court," Allied Chemical Corp. v. Daiflon, Inc., 449 U.S. 33, 36, 101 S.Ct. 188, 191, 66 L.Ed.2d 193 (1980) (per curiam), and will only be disturbed if the district court abused that discretion. We, therefore, review the district court's new trial order to determine whether the district court abused its discretion.

IV.

As an antitrust plaintiff seeking treble damages under section 4 of the Clayton Act, 15 U.S.C. § 15 (1976), American must prove three elements: (1) an antitrust violation, in this case a violation of section 2 of the Sherman Act; (2) fact of damage or injury; and (3) measurable damages. Danny Kresky Enterprises Corp. v. Magid, 716 F.2d 206, 207, 209 (3d Cir. 1983); Deaktor v. Fox Grocery Co., 475 F.2d 1112, 1116 (3d Cir.), cert. denied, 414 U.S. 867, 94 S.Ct. 65, 38 L.Ed.2d 86 (1973). It is upon the first two elements, proof of a violation of section 2 of the Sherman Act and fact of injury, that this case turns.

A.

To prove a violation of section 2, American must prove either monopolization or attempted monopolization. Both monopolization and attempted monopolization claims require American to present sufficient evidence to permit a jury to find that the defendant possessed the requisite market power necessary to constitute a monopoly. The market power analysis begins with a definition of the relevant product market for the particular product, United States v. duPont Co., 351 U.S. 377, 393, 76 S.Ct. 994, 1006, 100 L.Ed. 1264 (1956), and is an element of a section 2 violation that plaintiff must establish to prevail. Without a definition of the relevant market, the defendant's ability to exclude competitors cannot be determined. Walker, Inc. v. Food Machinery, 382 U.S. 172, 177-78, 86 S.Ct. 347, 350, 15 L.Ed.2d 247 (1965); Edward J. Sweeney Sons, Inc. v. Texaco, 637 F.2d 105, 117 (3d Cir. 1980), cert. denied, 451 U.S. 911, 101 S.Ct. 1981, 68 L.Ed.2d 300 (1981); Coleman Motor Co. v. Chrysler Corp., 525 F.2d 1338, 1348 (3d Cir. 1975). The outer boundaries of a product market are determined by the reasonable interchangeability of use between the product itself and substitutes for it. Brown Shoe Co. v. United States, 370 U.S. 294, 325, 82 S.Ct. 1502, 1523, 8 L.Ed.2d 510 (1962); duPont Co., 351 U.S. at 393, 76 S.Ct. at 1006. Within a broad product market, submarkets, which constitute product markets for antitrust purposes, may exist. Brown Shoe, 370 U.S. at 325, 82 S.Ct. at 1523. To establish that "thermal bearings" comprised a relevant product market or submarket, American, therefore, had to prove that a significant number of potential purchasers did not consider the bearings manufactured by American and Litton reasonably interchangeable with bearings produced by other bearing manufacturers. Evidence of "industry or public recognition of the submarket as a separate economic entity, the product's peculiar characteristics and uses, unique production facilities, distinct customers, distinct prices, sensitivity to price changes, and specialized vendors" must be presented. duPont Co., 351 U.S. at 393, 395, 399-40, 76 S.Ct. at 1006, 1007, 1009; Brown Shoe, 370 U.S. at 327, 82 S.Ct. at 1525; Edward J. Sweeney, 637 F.2d at 117. American's evidence on this point was unpersuasive and failed to rebut Litton's evidence that many manufacturers were competitors in the market for bearings in baghouses and precipitators. Litton could not have had market power in the market established by its evidence, and a verdict predicated on the market American sought to prove would be against the weight of the evidence.

Instead, even at this stage in the litigation, the precise product market that American seeks to define is ambiguous. At trial and in its brief, American sought to establish that the relevant product market was a narrow one, limited to those slide bearings which operate at "400 degrees Fahrenheit, 3,000 pounds per square inch and 3 per cent coefficient of friction." At oral argument, however, American asserted that the relevant product market consists of those bearings used at the support points of all precipitators that operate above 250 degrees internal temperature" (Transcript of Oral Argument filed November 30, 1983, at 12-13). American's position apparently is that they should prevail and the jury's verdict reinstated if evidence could support a finding that either product market existed. We disagree. Instead, "we hold an antitrust plaintiff in an appeal to the theory advanced at trial." Edward J. Sweeney, 637 F.2d at 117. Accordingly, we review the evidence to determine whether American presented sufficient evidence to enable a jury to find that a submarket, consisting of slide bearings which operate at 400 degrees Fahrenheit, 3000 p.s.i., and 3% coefficient of friction, exists.

The only evidence on which the jury could have found that such a market existed was Dr. Bowman's testimony. As noted above, see supra note 14, Dr. Bowman's testimony was self-contradictory. On the other hand, the rest of the evidence strongly suggests that the bearings of both American and Litton competed in a far broader market. The coefficient of friction parameter best illustrates the problem. An examination of the specifications for thirteen jobs indicates that only two of the thirteen called for bearings capable of operating with a coefficient of friction of 3% (3800a). The coefficient of friction specifications, instead, cover a range from 3% to 15%, with the majority falling in the 6% to 10% range (3800a). One of American's experts, Dr. Roll, after examining specifications provided by American and specifications selected for his review by United Engineers, a large construction design company which designs precipitators, determined that the typical design specifications covered a broad range of temperature, pressure, and friction parameters. Roll concluded that:

"The actual service load conditions depend upon the design specifications for the particular structure under consideration. Typical service load conditions for power plant requirements, for example, specify temperature of 350° F to 500° F, loads equivalent to bearing pressures of 2000 psi to 6000 psi, and bearing areas of approximately 5 ins. x 5 ins. to 8 ins. x 8 ins. Typical required coefficients of friction range from 3% to 15%, with the majority in the 6% to 10% range." (Emphasis added.)

(2479a). Moreover, specifications from fifteen jobs on which American submitted bids between 1976 and 1979 demonstrate that a submarket consisting of 400° F., 3000 p.s.i., and 3% coefficient of friction did not exist. Instead, each job involved a potential sale to a manufacturer of precipitators or baghouses and each involved performance parameters different from 400° F., 3,000 p.s.i., and 3% coefficient of friction. Only two of the fifteen specifications required a coefficient of friction as low as 3%. In contrast, several of the specifications called for coefficients of friction of 10% or greater (Supp.App. at 101a, 103a, 110a). Because precipitator and baghouse specifications typically require bearings to operate at coefficients of friction higher than 3%, bronze and meehanite bearings, which cannot provide a 3% coefficient of friction but which can and do satisfy specifications for 10% and above, belong among competing products in the relevant market (583a, 588a, 2014a). The tabulation of slide bearing costs submitted by one precipitator design company, Belco Pollution Control Corporation, to Mr. Hudson demonstrates that meehanite competes with the Teflon bearings. Of eight precipitator jobs listed by Belco, four specify that the slide bearings used were not Teflon at all but meehanite (1337-38a, 1450a, 1452a). Moreover, American's president, Mr. Roman, admitted that the Cosmec Company manufactured bearings that routinely competed with those manufactured by Litton and American. Cosmec, a manufacturer of Teflon, bronze, and meehanite bearings, routinely bid for precipitator jobs calling for bronze and meehanite (604a-05a, 611a). Despite Mr. Roman's admission, American defined the relevant market to exclude bearings manufactured by Cosmec that routinely competed with bearings manufactured by Litton and American.

In addition, data supplied by American Air Filter, another precipitator design company, indicates that every single precipitator job included in its tabulation used Fluorogold slide bearings, a Teflon bearing manufactured by Fluorocarbon (194a). Wheelabrator-Frye, a major designer of precipitators and baghouses (3373a-74a), specified "self-lubricating slide bearing plates similar to or equal to type FC1010CS as manufactured by the Fluorocarbon Co." for use in its baghouses (3120a). Neither Fluorocarbon nor its products, however, appear in the narrowly defined submarket that American defined. Such relevant submarket, therefore, failed to account for a competitor whose Teflon slide bearings were used in every precipitator designed by one of the industry's major manufacturers and designated as the standard by a second manufacturer.

Even if Dr. Bowman's testimony was properly before the jury, on this record, a verdict predicated on a submarket for bearings capable of meeting the specifications of 400° F., 3000 p.s.i., and 3% coefficient of friction is clearly against the weight of the evidence and would constitute a seriously erroneous result. 6A J. Moore, Moore's Federal Practice ¶ 59.08[5], at 59-147 (2d ed. 1983). A new trial was therefore necessary, and was certainly not an abuse of discretion.

B.

A similar problem exists with respect to American's evidence establishing injury-in-fact. Even if it established an antitrust violation, to prevail American also must establish that the violation was a material cause of some injury to its business. Zenith Radio Corp. v. Hazeltine, 395 U.S. 100, 114 n. 9, 89 S.Ct. 1562, 1571 n. 9, 23 L.Ed.2d 129 (1969); Van Dyk Research Corp. v. Xerox Corp., 631 F.2d 251, 255 (3d Cir. 1980), cert. denied, 452 U.S. 905, 101 S.Ct. 3029, 69 L.Ed.2d 405 (1981); Rea v. Ford Motor Company, 497 F.2d 577, 589 (3d Cir.), cert. denied, 419 U.S. 868, 95 S.Ct. 126, 42 L.Ed.2d 106 (1974). The evidence "linking the illegality and the injury must be more precise than that needed to establish the amount of damages." Van Dyk Research, 631 F.2d at 255; Rea, 497 F.2d at 589.

Unable to secure direct evidence of causation, American resorted to circumstantial evidence. American offers three instances of how dissemination of Litton's test memorandum allegedly caused injury to its business. First, the president of American, Dr. Roman, testified that shortly after developing the "Hi-Load" bearing he was well received by potential purchasers. After dissemination of Litton's memorandum, however, the reception turned "very, very cold" (405a). Second, American points to the fact that because bearings cost $130. each and that bearing failure could cost the companies approximately $200,000., a jury could reasonably infer that an engineer would not specify a bearing that a reliable source indicated would fail (Transcript of Oral Argument, filed November 30, 1983, at 30-31). Third, American notes that it lost two specific jobs immediately after Litton circulated the test report, even though American's bids were substantially lower than Litton's (636-46a). American argues that the jury was entitled to infer from this circumstantial evidence that Litton's conduct was a material cause of American's injury.

In Edward J. Sweeney, 637 F.2d at 116, this court stated that "[i]nferred factual conclusions based on circumstantial evidence are permitted only when, and to the extent that, human experience indicates a probability that certain consequences can and do flow from the basic circumstantial facts . . . . [A]ssuming a causal connection between two events merely because one follows the other" is insufficient. Id. We believe that American's evidence on this point was sufficiently weak that a new trial could appropriately have been granted on this ground as well, because the jury's verdict on this point was against the weight of the evidence and constituted a miscarriage of justice.

American failed to offer any supportive evidence that the cool reception Dr. Roman received in the industry was attributable to dissemination of the Litton memorandum. Moreover, American did not produce any evidence to support its assertion that an engineer would not specify a bearing that a reliable source indicated would fail. Instead, there was substantial evidence to the contrary from potential customers who testified that their refusal to purchase American's Hi-Load bearing was for reasons unrelated to Litton's memorandum. Mr. Fred Clements, a structural engineer supervisor for a major manufacturer of precipitators and baghouses, Research-Cottrell, testified that American was not on its approved vendor list because American had not supplied sufficient engineering data and because Research-Cottrell had experienced trouble with a sheet Teflon bearing similar to the Hi-Load bearing in the past. Similarly, Mr. John Rupak, a purchasing agent for Wheelabrator-Frye, testified that it stopped soliciting bids from American because American failed to comply with Wheelabrator-Frye's standard certifying procedure. Wheelabrator-Frye required bearing manufacturers to submit neutral laboratory data certifying that the bearing would meet their required temperature and pressure conditions (912-17a). Finally, Mr. Robert Baker, manager of quality assurance and control at Combustion Engineering, another precipitator and baghouse manufacturer, testified that Combustion Engineering would not award any jobs to American until American provided sufficient information concerning the capabilities of its Hi-Load bearing, information American did not submit (2076-79a).

Finally, the record included substantial evidence that American, despite being the low bidder on two jobs for United Oil Products, lost the jobs to Litton for reasons unrelated to the Litton memorandum. Dr. Roman admitted that American's bid for one of the two jobs was late and for a bearing of the wrong size. Moreover, a letter introduced into evidence indicated that American believed these bids were lost because of an asserted conflict of interest between United Oil Products and another bearing manufacturer, the Allan P. James Company, not because of Litton's memorandum (453-56a, 1926-28a).

Although American did not have to present uncontroverted evidence to prevail, it did need to demonstrate a "probability that certain consequences can and do flow from the basic circumstantial facts." Edward J. Sweeney, 637 F.2d at 116. In light of the explanations offered by United Oil Products, and the limited evidence offered to substantiate American's allegations, we conclude that a new trial was proper on the ground that the jury's verdict, premised on the conclusion that Litton's memorandum caused American's damages, was against the weight of the evidence and would have resulted in a miscarriage of justice.

Accordingly, the March 9, 1983, judgment of the district court (5974a) will be affirmed.

* * * * * *

[Dr. Bowman] Certainly. Thermal bearings are bearings which are slide bearings which operate at about 400 degrees Fahrenheit, 3000 pounds per square inch and 3 percent coefficient of friction."