ST. LOUIS — Shota Imanaga is officially back. And a new, but familiar face in the bullpen is gone. 

The Cubs announced on Thursday morning that they activated Imanaga off the injured list and designated right-handed reliever Michael Fulmer for assignment to make room on the active roster. 

Imanaga suffered a left hamstring injury on May 4 against the Milwaukee Brewers. He made three rehab appearances this month – two with the Arizona Complex League Cubs and one with Triple-A Iowa. Cubs manager Craig Counsell announced on Monday that Imanaga would start the finale against St. Louis. 

Imanaga takes the spot of right-hander Ben Brown in the rotation, who has struggled as of late in the majors. He has been the co-ace of the Cubs’ rotation the last two seasons, going 18-5 with a 2.89 ERA over 37 starts.

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Imanaga has made eight starts this season, tossing 44.2 innings with a 2.82 ERA. The Cubs’ rotation struggled in Imanaga’s absence, posting a 4.91 ERA that was the third worst in MLB. Before his injury, the Cubs’ rotation had a 3.44 ERA, the fifth best in MLB.

The Cubs will look to Imanaga for a series split on Thursday afternoon in St. Louis.

Fulmer had been solid in his two outings with the Cubs, pitching three scoreless innings in that span.

“Michael did a really nice job, and we’re hopeful that we could keep him in the organization. He’s got to go through a process here,” Cubs manager Craig Counsell said before Thursday’s matinee. “But we kind of mapped this chain of moves out, I guess is the best way to say it. And nothing kind of sidetracked us from that path. So this is where we landed up.”

The Cubs added Fulmer to the big-league bullpen Monday when they optioned Nate Pearson to Iowa.

Fulmer spent the 2023 season with the Cubs before undergoing Tommy John surgery. He spent time with the Boston Red Sox this season before being designated for assignment in April. He then signed a minor-league deal with the Cubs on April 22 and spent a couple months pitching for the team’s Triple-A affiliate.