According to newly filed court documents, television network Al-Jazeera relied on a “highly reputable law firm in Washington” to buttress claims about athletes' use of performance enhancing drugs that are now at the center of a contentious defamation lawsuit.

The source of those claims—aired in a 2015 documentary by now-defunct Al-Jazeera America—was Charlie Sly, a 31-year-old who was presented as a pharmacist and said he supplied performance-enhancing drugs to high-profile athletes.

But which law firm backed him up?

Davis Wright Tremaine, which served as Al-Jazeera's pre-broadcast counsel?

Or Gibson, Dunn & Crutcher, which former NFL quarterback Peyton Manning hired to pursue his legal options in the wake of the Al-Jazeera documentary, which included a disputed allegation that he had obtained human growth hormone after a neck injury?

That question now hangs over litigation pending in federal court in Washington, D.C., where major league baseball players Ryan Zimmerman of the Washington Nationals and Ryan Howard, formerly of the Philadelphia Phillies, sued Al-Jazeera for defamation in 2016.

According to a brief filed in the case May 4 by the athletes' lawyers at Quinn Emanuel Urquhart & Sullivan, the firm in question is Davis Wright Tremaine. Partners at Davis Wright, serving as Al-Jazeera's pre-publication counsel, “reinforced” the network's “belief in Sly's credibility” after they engaged in pre-broadcast discussions about his allegations with Gibson Dunn partners, the brief says.

In the the same filing, Quinn Emanuel's William Burck also notes that: “Al Jazeera has claimed that this source is an attorney from Gibson Dunn.” But, the memorandum states: “That is incorrect.”

Davis Wright partner Constance Pendleton, who represented Al-Jazeera, did not return a call seeking comment.

Nor did Chantale Fiebig, a partner in the D.C. office of Gibson Dunn, who has filed a motion under seal for the firm in the pending federal suit against Al-Jazeera. The American Lawyer reported in 2015 that former NFL quarterback Manning had hired Gibson Dunn's Theodore Olson in the wake of the Al-Jazeera report.

The ball players' lawyers at Quinn Emanuel declined to comment beyond what was in their brief. Michael Hynes, a partner in the New York office of DLA Piper who is defending Al-Jazeera in the case, declined to comment.

In their complaint, the two ball players say Al-Jazeera ignored red flags about Sly's doping claims. The Al-Jazeera documentary, “The Dark Side: The Secrets of Sports Dopers,” included Sly's assertions even though he had recanted prior to its broadcast, the athletes allege.

The ball players previously asked U.S. District Judge Ketanji Brown Jackson of the District of Columbia to compel Al-Jazeera to produce documents about its ratings, its financial investment in the documentary, its organizational charts, its staff members' texts and additional documents about Sly.

For its part, Al-Jazeera has denied the lawsuit's allegations, arguing in a motion to dismiss that the documentary did not contain actionable defamatory statements about Zimmerman or Howard, because “the pertinent representations are not reasonably capable of conveying a defamatory meaning.”

The network also argued that the ballplayers' complaint fails to plead facts that would support an inference of actual malice, a necessary component since the athletes qualify as public figures.

In a March 2017 order, however, the judge rejected Al-Jazeera's motion to dismiss, concluding that “the complaint that Zimmerman and Howard have filed contains sufficient allegations to state defamation and false light claims.”

In the May 4 filing, the ballplayers' lawyers are seeking to have the judge compel Al-Jazeera's lawyers at DLA Piper to produce documents that they say were “improperly withheld on privilege grounds.”

The athletes provided a detailed—though partially redacted—chronology of pre-broadcast communications between Al-Jazeera's then-counsel from Davis Wright and lawyers at Gibson Dunn. They say that in early December 2015, shortly after hearing from his agent that an Al-Jazeera reporter expected the network would air allegations about his drug use, Manning, one of the NFL's biggest stars, retained Gibson Dunn to provide legal advice and provide a legal strategy and response to the false claims.

By the middle of the same month, Gibson Dunn contacted Al-Jazeera's outside counsel at Davis Wright to discuss the allegations Al-Jazeera was threatening to broadcast claims about the Manning family, the memorandum says. Davis Wright had provided Al-Jazeera with extensive legal advice concerning Davis Wright's overall assessment of Sly's credibility, the athletes assert.

“This advice was based, in part, on an investigation conducted by two DWT partners, Robert Corn-Revere and Constance Pendleton,“ the memorandum states. The two Davis Wright partners “without the involvement of Al Jazeera reporters—engaged Gibson Dunn in a series of communications during which Corn-Revere and Pendleton pressed Mr. Manning's lawyers for additional information concerning Sly's allegations” about Manning's alleged use of performance enhancing drugs.

“In the course of those discussions, Corn-Revere and Pendleton quickly learned that several of Sly's most outrageous claims about Mr. Manning were false and incorrect,” the memorandum states. Davis Wright's Pendleton warned Al-Jazeera that it needed additional information and issued a recommendation that the network's reporters reach out to medical professionals to check on the allegations—advice the reporters heeded. “DWT also provided Al Jazeera with its legal conclusions and mental impressions about Sly and his credibility as a source,” the memorandum states.

Ultimately, Pendleton advised Al-Jazeera “that Sly was credible,” according to the ball players' memorandum. The reasons why she may have reached those conclusions are obscured by the redactions in the brief.

“Given that Al Jazeera has raised the affirmative defense of lack of actual malice and is attempting to prove that defense by relying upon confidential communications and legal advice provided by DWT, Al Jazeera has put the advice of counsel at-issue in this litigation and has, therefore, waived any attorney-client privilege or work product protections over the communications that pertain to this topic i.e., Sly's credibility,” the ball players' memorandum brief argues.

The memorandum asks the judge to compel Al-Jazeera to “produce all documents and communications that have been withheld, redacted, or clawed back that relate to Sly's credibility.”

Earlier this spring the court ordered Al-Jazeera to provide a privilege log identifying documents that DLA Piper had “inadvertently” disclosed to opposing counsel at Quinn Emanuel. The court wanted the log so that the network's privilege claims could be assessed. At the time, DLA's Hynes said his client had complied with the order.

Since then, on April 25, the court modified its prior order to “expressly preclude the review of documents after counsel receives notice of their inadvertent production”—precluding Quinn Emanuel from reviewing the documents that DLA mistakenly disclosed.