The Chicago Cubs placed closer Adbert Alzolay on the 15-day injured list Monday because of a forearm strain and called up their top prospect, outfielder Pete Crow-Armstrong.
The Cubs also activated reliever Michael Fulmer from the IL before the opener of a three-game series at Colorado.
The loss of Alzolay is a big blow for Chicago, which is fighting for playoff positioning in the NL standings. Alzolay has been the team's most dependable reliever, going 2-5 with a 2.71 ERA and 22 saves in 25 chances during a breakout season.
"We'll fill the gap with some of the guys we have down there," manager David Ross said of the closer role.
The 21-year-old Crow-Armstrong, meanwhile, is ranked 15th in ESPN prospect guru Kiley McDaniel's latest top 50 prospects. He compiled an .876 OPS split between Double-A and Triple-A this year, including 20 home runs and 37 stolen bases. He's considered one of the best defensive center fielders in the minor leagues and will likely get a chance this week to roam spacious Coors Field, where the Cubs play a three-game series against the Rockies.
"He earned the callup," Ross said. "Big outfield here, definitely can play some defense, steal a base. He'll get some starts mixed in; he can definitely help us out."
Crow-Armstrong was drafted by the Mets in the first round in 2020, then traded to the Cubs the next season in a deal for shortstop Javier Baez. Over three minor league seasons, he has hit .301 with an .892 OPS.
Crow-Armstrong is the likely long-term center fielder for the Cubs and will be given a chance to help them in the pennant race this year. Chicago currently holds the No. 2 seed in the NL wild-card race.
The Associated Press contributed to this story.