Former major league pitcher Roger Clemens, center, arrives at federal court in Washington on Thursday. (Charles Dharapak/Associated Press)

Roger Clemens’s chief accuser confided in a former Baltimore Orioles infielder years ago that he was keeping medical waste from the steroid injections he gave big league ballplayers, according to courtroom testimony.

The retired first baseman, David Segui, reluctantly took the stand in Clemens’s perjury trial Thursday as federal prosecutors tried to undo some of the damage done to their star witness, former strength coach Brian McNamee.

Testimony from Segui, who worked out with McNamee, was intended to bolster the strength coach’s assertion that he was not out to get Clemens or to make a name for himself when he saved needles, gauze and cotton balls after allegedly injecting Clemens.

McNamee is the only witness with firsthand knowledge of Clemens’s alleged use of performance-enhancing drugs. Clemens is charged with perjury, making false statements and obstruction of Congress for denying that he ever used steroids or human growth hormone in his 2008 testimony before a House panel.

Throughout the trial in federal court in the District, now in its sixth week, defense attorney Rusty Hardin has suggested that McNamee confided in federal agents about the star pitcher’s use of performance-enhancing drugs to avoid going to prison. Hardin also suggested that McNamee belatedly fabricated physical evidence against Clemens for financial gain.

But Segui backed up McNamee’s testimony that he saved the medical waste to placate his wife long before the strength coach began cooperating with federal agents in 2007. Segui told jurors that in 2001 McNamee told him about marital troubles he was having in part because of his demanding work schedule as Clemens’s personal trainer.

“The relationship between Roger and Brian had put stress on their married life. He said that she had raised the idea of keeping evidence. He mentioned that he kept darts to get his wife off his back,” Segui said, using a slang term for small needles.

Under cross-examination, Segui acknowledged that McNamee did not specifically say that the so-called darts belonged to Clemens, and said he had no direct knowledge of Clemens using steroids.

“All I know is what I was told on the phone. I never saw it. I never asked to see it. I don’t know,” Segui said. “He said, ‘I’ve kept some darts,’ so I knew there were multiple players.”

Defense attorneys had argued against allowing Segui to testify, opposing what they called “rank hearsay statements” in a court filing. And Assistant U.S. Attorney Courtney Saleski told the judge presiding over the case that Segui, an admitted steroid user, did not want to participate despite a subpoena.

But U.S. District Judge Reggie Walton cleared the way Thursday for prosecutors to question Segui and one of McNamee’s former clients to give the government a chance to back up the strength coach’s testimony. For days last week, the strength coach was aggressively questioned by Hardin about his changing story, lies to federal agents and exaggerations to investigators.

When jurors had an opportunity to submit questions for McNamee, one wanted to know: “Why should we believe you when you have shown so many inconsistencies in your testimonies?”

Walton decided not to ask that juror’s proposed question, telling attorneys in a private conference at the bench, according to the court transcript: “I won’t ask that, that’s for them to decide.”

The Associated Press contributed to this report.