The Cubs placed reliever Manny Rodríguez on the 10-day injured list (shoulder inflammation) prior to Friday's series opener against the Brewers.
In a corresponding move, the club reinstated lefty Adam Morgan from the bereavement list.
Rodríguez made his big-league debut at the end of July following a promotion from Triple-A Iowa. The right-hander holds a 6.11 ERA in 20 appearances, striking out 16 with 12 walks in 17 2/3 innings.
He's allowed 11 runs (eight earned) in his last four appearances.
Rodríguez, who wields a fastball that touches 100 mph, is part of the Cubs' bullpen plans heading into 2022. The 25-year-old represented the Cubs at the Futures Game weeks before his promotion.
Morgan went on the bereavement list last Friday. He's been one of the Cubs' most reliable relievers over the last month.
In 15 appearances since August, the veteran holds a 2.25 ERA, allowing three earned runs in 12 innings.