Yankees left-hander Andy Pettitte completed a successful bullpen session on Friday. Pettitte threw 25 pitches off the mound about four hours before the start of Friday night's Yankees-White Sox game. He'll throw another session as soon as Sunday. "This was progress, this was definitely progress for us," manager Joe Girardi said. "He's better than he was 10 days ago. I can't really tell you how much more or less, but today was a good day, that's all I can say." The Yankees have admitted that the best-case scenario would see Pettitte return in mid-September.