"We're not sure how long he'll be out," manager Eric Wedge said. "We're waiting to get MRI results and are hopeful it is not too serious."
Carmona was injured as he ran to cover first base in the third inning of Cleveland's 13-9 loss to the Texas Rangers on Friday night. He threw one pitch to the next batter, then left the game. The right-hander allowed six runs over two innings, hiking his ERA from 2.25 to 3.10.
The Indians are concerned about Lewis's drop in velocity and believe the 24-year-old can regain speed and command by working on a few fundamentals in his delivery.
"He was doing a decent job, but we need to get him back to the way he was last year," Wedge said of Lewis, who was 0-2 with a 3.58 ERA in 20 games in relief. He went 1-1 with a 2.15 ERA in 26 outings as a rookie a year ago.
"We need a guy like him that we can count on at the back end," Wedge continued. "He's got a lot of gusto out there, he's healthy, but he's not the pitcher we know he can be."
Carmona's injury occurred at about the same time that right-hander Jake Westbrook was pitching six scoreless innings during an injury rehabilitation assignment at Double-A Akron. Westbrook has been sidelined since April 22 with a strain near his left ribcage.
The 33-year-old Elarton was 1-2 with a 2.45 ERA in 15 relief appearances at Buffalo. He has a 56-60 record with a 5.31 ERA, mostly as a starter for Houston, Colorado, the Indians and Kansas City. He was 14-14 with Indians in 2004 and 2005.
"Scott was close to making this ballclub out of spring training," Wedge said. "He's a strike-thrower with a lot of experience."
Mujica, 24, was 0-2 with four saves and a 4.15 ERA at Buffalo. He was called up by the Indians five times last season. Lewis is 0-2 with a 3.58 ERA in 20 games in relief for Cleveland this season.