Cleveland ace Corey Kluber, who won the 2014 AL Cy Young Award and is a top contender for the honor this year, had an MRI on Tuesday in Cleveland that confirmed he has a mild quadriceps strain.
The Indians say his timetable for returning to game activity is a week to 10 days, which could force the AL Central champions to delay his first playoff start. Cleveland's first playoff game is Oct. 6.
It's another blow for the Indians, who are already missing starting pitchers Carlos Carrasco and Danny Salazar.
"It's obviously not the best possible news, but it is a heck of a lot better than it could have been,'' manager Terry Francona said. "This will give him a chance to rest up and hopefully throw a couple bullpens. In the long run, that could help him.''
Cleveland is bumping right-hander Trevor Bauer back to the weekend. The Indians will start Zach McAllister, who has pitched almost exclusively out of the bullpen this year, on Wednesday against the Tigers. On Thursday, Ryan Merritt will make his first career start.
"Our objective always is to win, but we'll get to see everybody, we'll try to manage people's innings,'' Francona said. "We really need to keep our pitchers healthy so they can be productive.''
Salazar threw a bullpen session Monday, but Carrasco is out for the season.
Information from the Associated Press was used in this report.