Before Yankees left-hander Andy Pettitte retakes the mound in the Bronx, he took to the courthouse Wednesday morning in Washington to testify against his friend and former teammate Roger Clemens in Clemens' perjury case.

Yesterday, Pettite testified that "Roger had mentioned to me that he had taken HGH." He made the same claim in a congressional deposition in 2008, prompting Clemens to say that his friend "misremembers" their conversation.

Pettitte remains the key witness in the Clemens' trial, as prosecutors try to get Pettitte to admit that Clemens lied to Congress after denying using performance enhancing drugs.

Another key witness in the case is former trainer Brian McNamee, who worked with both Clemens and Pettitte in Texas during "happier times."  A photo was shown from the government of the three working out in Texas, while Pettitte describe the photo as "Mac, Roger and me."

Unlike Clemens, Pettitte has admitted using HGH in 2002 and in 2004, and says that he's regretted it both times he tried it and that it didn't help him at all, let alone it tarnished his name.

Neither Clemens or Pettitte acknowledged each other during the trial today, as both came in from opposite ends of the courtroom and left without even looking at each other.

While Clemens remains out of baseball, Pettitte is expected to return to the Yankees rotation this month, after making minor-league starts at 'AA' Trenton and 'AAA' Scranton.