Manager Fredi Gonzalez said Kimbrel would be day-to-day. He turned to setup man David Carpenter to record the final three outs in a 9-6 victory over the Philadelphia Phillies Monday at Citizens Bank Park.
Kimbrel said after the game that he's been bothered off and on by the issue since spring training. But he said it's not serious and he expects to be back on the mound soon.
"There's no reason to push it this early in the year,'' Kimbrel said. "It's something that doesn't really hinder me on the field. Being a pitcher, things get sore now and then. It's just a little uncomfortable. I'll take a few days off and be ready to go.''
Kimbrel, 25, has been the most dominant closer in the game over the past three seasons. He's a three-time All-Star, and last year he led NL relievers with a 1.21 ERA and 50 saves.
In 237 big league appearances, Kimbrel has averaged 15.2 strikeouts per nine innings. His 90.6 save percentage is third-best in history among relievers with at least 150 opportunities, behind only Eric Gagne and John Smoltz.
Kimbrel last pitched Friday and Saturday, recording back-to-back scoreless innings in wins over the Washington Nationals.
"From talking to Craig and the trainers, it's one of those things every reliever goes through over the course of the season,'' Gonzalez said. "Guys are hurt and banged up. If it's not the closer and we're in a save situation, nobody would even know. I'm not concerned at all.''