Manager Terry Francona said Carrasco was taken for a precautionary MRI. The Indians are hoping it's nothing serious.
"He kind of bruised it. He fell on it, but he initially felt it in the back," Francona said. "So that's why the medical people felt like let's just rule everything out. Hopefully it's just being precautionary, but we do want to get him checked out."
Carrasco, who was coming off a 12-strikeout performance in his previous outing, got hurt when he stumbled and fell while covering first base in the fourth inning. He finished the inning but was pulled after telling Francona his leg tightened.
Reliever Neil Ramirez took over to start the fifth. The Indians went on to lose 3-1.
Carrasco pitched four shutout innings and struck out four before being forced to leave. He is 2-2 with a 6.00 ERA this season.
The Indians are already missing starter Mike Clevinger, who is expected to be sidelined another two months with a back strain. The loss of Carrasco, a 17-game winner last season, for any period would be another blow to the three-time defending AL Central champions, who are not hitting well and are counting on their pitching to carry them.
The Indians are batting an AL-worst .210 and have gotten three or fewer hits four times this season.
The Associated Press contributed to this report.