Pettitte, 39, will take the ball in a 1 p.m. ET start against the Clearwater Threshers, a Phillies affiliate, at George M. Steinbrenner Field in Tampa, Fla.
"In A-ball, you don't always see people working the count, so 45 pitches could take a while," Yankees manager Joe Girardi said.
That was the case in Pettitte's last start, as the Yankees wanted him to throw two innings and 35 pitches but sent him back out for the third inning -- also against Clearwater. In that start, on Monday, Pettitte threw 26 of 32 pitches for strikes.
The Yankees continue to plan as though Pettitte is returning to the big leagues in May, and Girardi reiterated on Saturday that when the five-time World Series winner is ready, he will have a spot in the rotation.
That will mean bad news for someone in the Yankees' current starting five, but Girardi wasn't prepared to ponder how they'll figure it out.
"That's why we signed [Pettitte]; we're going to have to make an evaluation," Girardi said. "Ready is not just a pitch limit. Ready is how you're throwing the baseball, too. We have to evaluate that. It'll be harder for me to evaluate that, because I'm not going to see him.
"I trust the people that are making the decisions. We'll cross that bridge when we have to. Right now, we don't have to. We want the guys to just go out and throw the baseball the way they're capable."