The Yankees also activated Ivan Nova from the disabled list and relegated the right-hander to the bullpen.
Pettitte threw 45 pitches in three simulated innings and is scheduled to see doctors Monday to evaluate his fibula, which he broke in late June. If he is cleared to run, Pettitte thinks he may be able to speed up his return to the majors.
After throwing a bullpen session, Pettitte (3-3, 3.22 ERA) expects to throw another simulated game between Tuesday and Thursday in Boston.
The 40-year-old Pettitte could throw 60 pitches, and manager Joe Girardi would not rule out that the left-hander could pitch five days later, meaning he possibly could be on a mound at some point during the week of Sept. 17.
His return still may end up being closer to Sept. 24, which has been the presumed target date.
"I don't want to be stupid, but I didn't think I was going to come back and be as sharp as I am," Pettitte said. "I thought it would take a lot of bullpens and some game work obviously. But since my command has been so good, I think everybody's been comfortable just running me back out there with these simulated games as quick as we can."
The Yankees considered making Nova their starter for Sunday instead of Freddy Garcia, but now will wait and see. There is a good chance Nova (11-7, 4.92 ERA) could replace David Phelps or Garcia as a starter next week.
"We have always considered (Nova) a rotation guy," Girardi said.
Girardi nearly yanked Garcia from his scheduled start Sunday, because he was unhappy with the right-hander's failure to make it through the fifth inning in two of his last three starts. Phelps also has failed to go five innings in his last two starts.
However, Nova also struggled prior to going on the disabled list a couple of weeks ago with an inflamed right shoulder. In eight starts in the second half of the season, Nova is just 1-4 with a 7.28 ERA.
"He is in the bullpen for now," Girardi said. "Our bullpen has been used a lot lately, so we will put him down there for now and then we will make some decisions on whatever we decide to do."
Nova said he just wants to get back on the mound.
"If they think I should go to the bullpen for a couple of days, I go to the bullpen," Nova said.