Upon cross examination from Roger Clemens' attorney Wednesday New York Yankee pitcher Andy Pettitte acknowledged that it was fair to say that there was "50-50" chance he misunderstood Clemens say that he used human growth hormone 12 years ago, according to ESPN.

Clemens is currently on trial for perjury because he allegedly lied to congress about using performance enhancing drugs years ago.

Pettitte is a key government witness and his concession Wednesday could weaken the prosecution's case.

Tuesday, Pettitte had testified, "Roger had mentioned to me that he had taken HGH," which was the same claim he made in a congressional deposition in 2008.

Naturally, Pettitte was uncomfortable testifying against Clemens, who was his former teammate and one-time mentor. During the proceedings the former teammates sat on opposite ends of the courtroom and Pettitte refrained from looking in Clemens' direction.

By causing Pettitte to create some confusion as to what he heard, Clemens' attorney Michael Attanasio may have created the reasonable doubt needed to exonerate his client in this case.

This is mainly because the government's case will now rely primarily on the testimony of Brian McNamee, who worked as a strength coach for both Clemens and Pettitte and has said he injected both men with performance-enhancing substances.

Pettitte has acknowledged he received HGH from McNamee, but wasn't allowed to reveal that he was injected by McNamee because the judge ruled that information was inadmissible.

"I wish I never would've" taken HGH, said Pettitte. "If I hadn't done it, I wouldn't be here today."

Pettitte additionally referenced the only other time that he spoke with Clemens about his HGH use, leading up to the initial congressional hearings surrounding performance enhancing drug use in sports when the two were teammates on the Houston Astros in 2005.

Pettitte asked Clemens what he would say if reporters asked him about HGH use, to which Clemens responded, "What are you talking about?"

"He said, `My wife used it," said Pettitte.

"Obviously I was a little flustered," Pettitte said, "because I thought that he told me that he did."

Clemens has also acknowledged that his wife Debbie had been injected by McNamee.

During direct examination, Pettitte told prosecutors that he still considered Clemens a good friend but hasn't been able to talk to him for a long time because of the case. He also acknowledged the conflict he felt by testifying against a friend.

The stress that testifying against Clemens caused Pettitte to feel obviously showed in the courtroom.

Accordingly, the rest of the case will now hinge upon the testimony of Brian  McNamee, whose credibility has been questioned in the past and will assuredly be attacked by Clemens' attorney.

What do you think?