"He's just a little achy, and it just doesn't make sense at all for us to keep running him out there," Reds manager Bryan Price said after a 6-5 loss to St. Louis in 10 innings. "He was a little achy [Sunday]. I didn't want to say anything, but he was. By the time we knew there might be an issue, the damage was done yesterday.
"Our trainers say it's a day-to-day thing and that he could be ready to go soon. I'm not crossing him off our list for tomorrow by any means."
If the Reds had taken the lead in extra innings, Jonathan Broxton would have been called on to close for Cincinnati. Chapman's issue is the latest bad news for a bullpen that has allowed 17 runs in three losses over the past two days.
Chapman, a three-time National League All-Star, has been one of the Reds' most dependable relievers with a 2.82 ERA and 26 saves in 28 chances. On Friday, his Major League reliever record of 49-straight games with at least one strikeout ended when he notched a save vs. Colorado.