NEW YORK -- Andy Pettitte has a "small, persistent strain" of his left groin and will not throw off a mound for at least a week.
An MRI of Pettitte performed during the Yankees' game Monday night against the Tigers revealed the continued presence of the injury. Pettitte had thrown off flat ground in the outfield before the game, then moved to the bullpen where he threw approximately 40 pitches, off a half-mound and a full mound.
Afterward, Pettitte informed the Yankees that the same discomfort that caused to him to cut short a simulated game last Friday in Tampa had recurred, and he was taken to Columbia Presbyterian Hospital for an MRI the Yankees characterized as precautionary.
"They're basically doing this to set his mind at ease," a team spokesman said.
Pettitte, 38, originally suffered the injury in the third inning of a start against the Tampa Bay Rays at Yankee Stadium on July 18. At the time, the team expected Pettitte to miss 4-5 weeks of action, but earlier this week, manager Joe Girardi said Pettitte was "another two weeks at least" away from returning.
With this latest setback, it is unknown when Pettitte will be able to pitch again. He did not speak to reporters after his bullpen session, but released a statement.
"I'm feeling better," he said. "When I reach back 100 percent like when I'm trying to get a hitter out in a game, the groin area grabs."
The Yankees said Pettitte will continue to throw from flat ground but will do no mound work, including bullpen sessions or simulated games, for at least a week. That seems to preclude a return to action for at least three weeks, or roughly the first week of September.
At the time of his injury, Pettitte was enjoying the best start of his 16-year career with an 11-2 record and 2.88 ERA. On the day Pettitte got injured, the Yankees had a 58-33 record and led the AL East by three games. Since then, they have gone 14-13 and have fallen into a first-place tie with the Rays.