The Cubs lost a valuable member of their bullpen to the injured list Friday in Justin Steele.
Prior to Friday's series opener with the Cardinals, the club placed the lefty on the 10-day IL with a right hamstring strain.
The Cubs recalled lefty Brad Wieck from Triple-A Iowa in a corresponding move.
Steele, 25, exited Thursday's game against Washington with right hamstring tightness. After throwing 1 1/3 scoreless innings, he attempted a few warmup pitches in the top of the seventh, exiting after David Ross and a trainer checked on him.
Ross called Steele's strain "moderate." He joins Jason Heyward and Jake Marinsick on the IL with hamstring strains.
Ross said Heyward, who hit the IL Thursday, started light activities Friday.
Steele has emerged as a force out of the bullpen this season. In 11 appearances, the southpaw holds a 2.03 ERA and 1.05 WHIP, striking out 21 batters (seven walks) in 13 1/3 innings.
The Cubs bullpen has been one of the best in baseball this season, entering Friday fourth in ERA (3.16). The relievers have picked up a ton of slack as the rotation has struggled to pitch deep into games.
Wieck has thrown two scoreless innings in a pair of appearances with the Cubs this season, allowing one hit and one walk with three strikeouts. He's thrown 4 1/3 scoreless innings with Iowa, allowing a hit and three walks with seven strikeouts.
Wieck joins Rex Brothers and Andrew Chafin as lefties in the Cubs bullpen.