McCoy pulled his right hamstring while covering first base in Saturday's loss to Tampa Bay. Krol has been sidelined since June 21 because of left shoulder inflammation.
McCoy posted a 1.80 ERA in five appearances with the Tigers. Krol has a 4.32 ERA in 35 games for Detroit.
The Tigers are still without designated hitter Victor Martinez, who was out of the starting lineup Sunday night against the Rays. He also missed Saturday's game with a back issue.