Roger Clemens and his accuser, Brian McNamee, will be the main witnesses at a House hearing on the Mitchell Report after New York Yankees pitcher Andy Pettitte and two others were dropped Monday night.

Former Clemens teammate Chuck Knoblauch and convicted steroids distributor Kirk Radomski also were taken off the witness list for Wednesday's public session. One new witness was added Monday night: a lawyer who worked with former Senate majority leader George Mitchell to produce December's report on drugs in baseball.

But all attention will be focused on Clemens, a seven-time Cy Young Award winner, and McNamee, his former personal trainer, who alleged he injected the pitcher with performance-enhancing drugs.

"I guess it's showtime, isn't it?" Clemens' lead lawyer, Rusty Hardin, said in a telephone interview.

Earl Ward, McNamee's lead lawyer, declined to comment on the changes.

McNamee said in the Mitchell Report that he injected Clemens — who ranks eighth in major league history with 354 wins — with steroids and human growth hormone at least 16 times in 1998, 2000 and 2001. Clemens' denials of those allegations drew the attention of the House Committee on Oversight and Government Reform.

McNamee also accused Pettitte of using HGH — Pettitte acknowledged he did so for two days in 2002 to deal with an elbow injury. Before Pettitte spoke to committee lawyers under oath last week, Ward said he thought Pettitte would tell Congress he discussed HGH with Clemens between the 2001 and 2002 seasons.

With Monday's decision, Pettitte was spared the potentially difficult situation of having to deliver public testimony that could hurt the position of Clemens, a friend, past teammate and former workout partner. Portions of Pettitte's sworn deposition, though, may be read aloud at the hearing. And the committee's ranking Republican, Tom Davis of Virginia, said in an interview with Newsday that Pettitte's account matches McNamee's in most details.

Radomski — sentenced Friday to five years' probation after pleading guilty in April to distributing steroids and money laundering — has said he had no direct contact with Clemens. Knoblauch's knowledge appeared to be peripheral.

Pettitte gave his deposition last Monday, followed the next day by Clemens, and McNamee later in the week. Knoblauch, a four-time All-Star who played on the Yankees with Clemens and Pettitte and like them was named in the Mitchell Report, was interviewed by committee staff last month. Radomski had been scheduled for a pre-hearing interview with committee staff Tuesday.

All five originally were invited to testify Wednesday.

"Mr. Knoblauch and Mr. Pettitte answered all the Committee's questions and their testimony at the hearing is not needed," Davis and committee chairman Henry Waxman said in a statement. "Mr. Clemens and Mr. McNamee have also cooperated with the Committee in its investigation."

Following Pettitte's deposition, his lawyers asked the committee to excuse him from the hearing, a person familiar with the talks said, speaking on condition of anonymity because the negotiations weren't made public.

Pettitte's request to be excused was first reported by The New York Times on its Web site.

Pettitte's attorney, Jay Reisinger, declined to comment after the announcement, while a lawyer for Radomski did not immediately return a phone message left at his office Monday night.

"I'm not disappointed," said Knoblauch's attorney, Diana Marshall. "I know Chuck is not disappointed."

The new witness is Charles Scheeler, a partner with Mitchell's law firm, DLA Piper. According to the firm's Web site, Scheeler mainly works in commercial litigation and white collar criminal defense.

Asked about Scheeler's addition, Hardin said: "It's interesting. I look forward to hearing what he has to say."

Clemens' camp disputes several elements of the Mitchell Report's sections about him. Clemens said he repeated under oath during his closed-door deposition what he previously had said in various settings publicly: "I've never used steroids or growth hormone."

If the committee believes Clemens or McNamee made false statements under oath, it could ask the Justice Department to open an investigation. This is the same House panel that — after the Mitchell Report came out — asked Justice to look into whether 2002 AL MVP Miguel Tejada lied when he told committee investigators in 2005 that he never took performance enhancers and had no knowledge of other players using or talking about steroids. The FBI's field office in Washington is handling that inquiry.

"We've always known that one of the potential possibilities, one of the possible results of Roger testifying differently than the Mitchell Report, could be a criminal referral," Hardin said Monday, before the witness list was changed. "That's an option the committee's always had."

McNamee, for his part, arrived for his deposition with color photos of what his side says is evidence — and what Clemens' lawyers have called "manufactured" — that was turned over to the Justice Department last month. McNamee's lawyers say the items include used needles saved for several years and that, when tested, they will prove Clemens used performance-enhancing drugs.

While McNamee has been quiet, not speaking a word to reporters after his deposition, Clemens has been crisscrossing Capitol Hill, speaking with nearly half of the members of the committee on a two-day tour last week. The 45-year-old pitcher planned to meet with more lawmakers Tuesday, the day before he testifies under oath at the hearing.

Pettitte was supposed to be there Wednesday, too. Now the left-hander is free to get ready to head to spring training. Yankees pitchers and catchers are to report Thursday.

"Every witness should make the decision that's best for them," Hardin said Monday night. "Roger plans to be there and to answer every question fully and truthfully. Whatever anybody else did, that's their deal."