The 38-year-old veteran, who played catch on flat ground for five minutes before Saturday's 7-4 loss to the Royals, believes he can return to the starting rotation much sooner than that.
"It doesn't seem realistic to me at all right now, but I haven't gotten on a mound," Pettitte said before the game. "When I get on the mound, I'll be able to say, and hopefully I won't have any setbacks."
Manager Joe Girardi preached caution when told of Pettitte's expectations, noting the pitcher had yet to throw off of a mound.
"It's one thing to walk around; it's another thing to have to get off the mound and push," Girardi said of Pettitte, who spent 15 days on the disabled list in 2001 with a groin strain. "I'm very happy with the progress he's making and says he feels good. I'll feel a lot better once he throws off the mound and says he doesn't feel anything because that's where you're going to exert yourself in that area."
It is unclear when Pettitte will throw off of a mound. He said he will travel to Tampa on Monday -- presumably to continue rehabilitation -- and will rejoin the Yankees on July 30 when the team opens a three-game series against the second-place Rays.
Pettitte left his last start on Sunday against the Rays in the third inning when he felt pain in his groin. He was taken to New York Presbyterian Hospital for an MRI and diagnosed with a Grade 1 groin strain -- the least severe strain.
He said he felt no pain while playing catch from 60 feet on Saturday, making about 40 throws. He hopes to soon progress to long-toss -- throwing from a distance of 100 feet -- to increase his arm strength.
"I feel like this is pretty good that I'm throwing already," Pettitte said. "If I can start long-tossing in the next couple of days I don't think I'm going to lose much arm strength at all."
Pettitte, 38, is having one of the best seasons of his 16-year career. His 11 wins before the All-Star break marked his highest first-half total since 2003 and his 2.88 ERA matches his 1997 season ERA, his career-best as an American League pitcher. He had a 2.39 ERA for Houston in 2005.
Girardi isn't rushing Pettitte's return.
"If you go out and you try to do too much and feel it again then we're right back to where we were [last] Saturday, so be patient," Girardi said he told Pettitte in the dugout during Friday night's 7-1 win over the Royals. "When we put this behind us we want to put this behind us for the year."
Sergio Mitre was activated from the disabled list before Saturday's game against the Royals and was slated to start in place of Pettitte. Mitre, who was placed on the disabled list on June 15 with a strained left oblique muscle, was scheduled to make his first start since May 16. Reliever Jonathan Albaladejo was optioned to make room for Mitre.
Ian Begley is a regular contributor to ESPNNewYork.com. Information from The Associated Press was used in this report.