Chicago Cubs closer Craig Kimbrel was put on the injured list with elbow inflammation on Thursday ahead of a big series against the Milwaukee Brewers.
The Cubs also scratched infielder Javier Báez with lingering soreness in his left thumb.
Kimbrel hasn't pitched since allowing a three-run home run to Milwaukee's Christian Yelich in a 4-0 loss Sunday.
"He felt a little something pop up in that outing so just to be on the cautious side, we had an MRI done," Cubs president of baseball operations Theo Epstein said. "It showed everything is in place structurally. He just has a little inflammation.
"His elbow was pristine just like when we signed him, which is good news, but unfortunately we have to give him a few days without throwing to let it calm down," Epstein said.
Kimbrel had 42 saves for the World Series champion Boston last season, became a free agent and did not agree to a contract until reaching a $43 million, three-year deal with the Cubs on June 7.
He made his debut on June 27, earning his first save of the season with a scoreless ninth inning against Atlanta, then allowed five runs over his next two outings. The 31-year-old settled in and converting his next six save opportunities without allowing a run.
Kimbrel has a 5.68 ERA in 21 games with 26 strikeouts in 19 innings.
Chicago made the move retroactive to Monday, and Kimbrel is eligible to be activated for next Thursday's series finale at San Diego.
Báez hasn't played since jamming the thumb on a third-inning slide sliding into second base in the Cubs' 4-0 loss to Milwaukee last Sunday. X-rays on the thumb were negative, but manager Joe Maddon rested Báez in both games of an interleague set against the Mariners Monday and Tuesday.
Infielder David Bote was recalled from Triple-A Iowa to take Kimbrel's roster spot.