Pettitte, 35, was scratched from Wednesday's game against the Rays in St. Petersburg due to mild tightness in his left forearm. He went through Friday's full session at Legends Field with pitching coach Dave Eiland in attendance.
"I was able to stretch it out in the long toss," Pettitte said. "For me to back up my long toss like I did, I knew I wasn't going to have any problems, so I didn't even concern myself with when I was on the mound."
Pettitte remains on track to pitch on Monday against the Red Sox in Tampa. The Yankees expect Pettitte, their projected No. 2 starter, to be able to build to more than 90 pitches by Opening Day.
"I'm not concerned," Yankees manager Joe Girardi said. "As I said on Wednesday, it was so minor and he didn't feel anything the day before. We're just being overcautious and overprotective."
Pettitte said that he had no preference between pitching against Boston and throwing in a Minor League game.
"I couldn't care less, to tell you the truth," Pettitte said. "I just need to throw 60 pitches."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.