"When I heard four to five [weeks] I was thinking, 'Oh gosh,'" Pettitte said Tuesday before the Yankees played the Los Angeles Angels. "I hope it heals up quick. I don't know if it's realistic."
The 38-year-old All-Star, who was placed on the disabled list, was injured Sunday while throwing a pitch in the third inning against the Tampa Bay Rays. An MRI showed he had a Grade 1 strain, which is the mildest on a scale of 1 to 3. The move was retroactive to Monday.
Manager Joe Girardi said the problem with a groin injury for a pitcher is that once it has healed, strength must be rebuilt. Pettitte was told that he will have to take a week off to rest the groin before starting rehabilitation.
"That's going to be the tough part," said Pettitte who adopted Roger Clemens' extensive workout habits when they were teammates on the Yankees.
This is Pettitte's eighth trip to the DL -- his first since 2008. He was sidelined in 2001 with a groin strain.
Sergio Mitre will come off the DL to start in Pettitte's spot Saturday against Kansas City. Out since June 15 with a strained muscle on his left side, Mitre said he felt ready after pitching six innings in a rehabilitation outing for Triple-A Scranton/Wilkes-Barre on Monday.
Mitre made 27 starts for Florida in 2007 before having elbow reconstruction surgery in '08. He made nine starts for the Yankees last year.
"I'll pitch well for the next month then Andy comes back and he'll go back to doing what he's doing," Mitre said.
Pettitte is in the middle of one of the best seasons of his 16-year career. He is 11-2 in 18 starts and if the season was over his 2.88 ERA would match 1997 for his best ERA as an American League pitcher. He had a 2.39 ERA for Houston in 2005.
The Yankees also recalled right-hander Jonathan Albaladejo from Scranton, where he had a 0.96 ERA in 41 games. He converted 31 of 32 save chances, attributing his success to developing a four-seam fastball.
"We taxed our bullpen pretty good the last two days. It gives us a little protection," Girardi said.
Pettitte's injury came a day after A.J. Burnett cut both hands slamming open a set of double-doors in the clubhouse out of frustration. Burnett, lifted with no outs in the third inning Saturday, said he should make his next scheduled start. The bullpen threw 13 2/3 innings over the two days, but the Yankees did have a day off Monday.
The loss of Pettitte is a blow for the Yankees' rotation, which has been one of the keys to the team's success. CC Sabathia, Phil Hughes and Pettitte each have at least 11 wins, and Javier Vazquez has bounced back after struggling in April. Only Burnett has been inconsistent, going 0-5 in June before pitching well in two starts before the All-Star break.
Girardi said he wasn't too concerned about Pettitte being out for five weeks because the team had depth in the back end of the rotation with Mitre and Chad Gaudin competing for the fifth starter's spot during spring training.
Girardi said the one person who will not make a spot start was Joba Chamberlain, who has struggled with his command at times working as the eighth-inning setup man.