With a healthy effort on Sunday in a Minor League game in Tampa, Girardi said, Pettitte can solidify his spot in the starting rotation.
Girardi expects Pettitte to be ready to pitch against the Tampa Bay Devil Rays next Saturday.
"Everything's great," Girardi said. "It puts him on schedule to be in the first rotation."
Pettitte, who had an abbreviated spring because of various ailments, is expected to be evaluated after his game on Sunday.
The Yankees also demoted six players on Friday, putting them at the 25-man roster with which they plan to open the season on Monday.
Five of those who were called into Girardi's office and demoted were pitchers: right-handers Scott Patterson, Darrell Rasner, Jose Veras and Edwar Ramirez, and lefty Kei Igawa.
The other player was second baseman Nick Green, who hit .185 in his bid to make the club.
Girardi said that it was particularly difficult to demote Patterson, who pitched 7 2/3 scoreless innings in eight appearances this spring.
"Brutal," Girardi said. "But he had a good attitude. He said he would go out and get people out in Triple-A [Scranton] and be ready if we need him. He had an amazing camp."
Those benefiting from Friday's moves include relievers Brian Bruney, who had a 2.00 ERA this spring, striking out 12 in nine innings, and Jonathan Albaladejo, whose ERA was 4.32 in 8 1/3 innings, with nine strikeouts.
But the moves left the Yankees without an established long reliever. Girardi seemed unfazed, saying that the club can do without one early because everyone is fresh. He said that the Yankees could bring up a long reliever when the bullpen begins to get overworked.
Charlie Nobles is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.