A MRI taken on Monday at New York-Presbyterian Hospital revealed the injury, as Teixeira was forced to leave New York's 8-7, 11-inning loss to the Blue Jays after running the bases in the fourth inning.
"It could be as little as a week, it could be two weeks," Teixeira said. "I don't really know. I just know that the MRI showed a strain."
With the roster expanding to 40 players on September 1, the Yankees do not plan on placing Teixeira on the disabled list. Instead, they will likely employ a tag team of Nick Swisher, Eric Chavez, Casey McGehee and Steve Pearce, who was acquired from the Pirates yesterday, at first base.
Teixeira, 32, is hitting .255/.335/.478 with twenty-three home runs in one hundred nineteen games this season. While the exact recovery timeframe for the injury is unknown, it should be noted that Yankee shortstop Derek Jeter missed three weeks with a similar injury last season.