Indians right-hander Fausto Carmona, who started Friday night's game against the Texas Rangers, left the ballgame with a left hip strain and is day to day.
With no outs in the third inning, Carmona appeared to be hobbling as he tried to make a play at first base.
Carmona made one pitch to the next batter, Brandon Boggs. But then the Indians training staff came to the mound to examine him. He left the game minutes later, and Jorge Julio came on to replace him.
"We'll know more [Saturday]," manager Eric Wedge said. "He'll get an MRI. Until we take a look at that, we're really not going to know much."
Carmona was unavailable for comment.
"Obviously, he wasn't able to stay in the game," Wedge said. "So it's fairly serious. We're just hopeful when the picture comes back that it's not too serious."
Before the ballgame, the Indians activated closer Joe Borowski from the 15-day disabled list and designated left-hander Craig Breslow for assignment.
Justice B. Hill is a senior writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.