CHICAGO — The Cubs were dealt another blow to the rotation Monday, announcing lefty Shota Imanaga is headed to the 15-day IL with a strained left hamstring.

Right-handed reliever Gavin Hollowell was recalled from Triple-A Iowa in a corresponding move.

Imanaga exited his start against the Milwaukee Brewers in the sixth inning Sunday, grabbing the back of his left leg while running to cover first base.

“After the way he walked off the field, we knew it was going to be an IL (stint),” Cubs manager Craig Counsell said before the team’s series opener against the San Francisco Giants.

Counsell added that despite the setback, Imanaga was in good spirits when he arrived at Wrigley Field for imaging on his leg.

“He feels pretty good today. That’s just in our conversation — I hope that’s good news,” Counsell said. “It’s better than feeling bad, but we have to let the doctor look at him and let the imaging guide us.”

Imanaga had not allowed a run in the game but was charged with two earned runs after Julian Merryweather inherited Imanaga’s baserunners. The 31-year-old ace had a previous injury scare on April 28 in Pittsburgh, leaving his start abruptly in the sixth inning with leg cramps in both of his quadriceps.

Imanaga has been a cornerstone in the Cubs’ rotation since his debut in 2024, and the team has a 28-9 record all-time when he takes the mound. This season, he owns a 2.82 ERA with 34 strikeouts in 44 2/3 innings pitched.

The Cubs are now temporarily without both top starters as Justin Steele is out for the season with a flexor tendon injury that required surgery.

While Imanaga recovers, the Cubs have a decision to make with the rotation moving forward. His next start was scheduled for Saturday against the Mets in New York City. However, Counsell and his staff are not rushing to fill the empty slot.

“We’re talking about Saturday and it’s (only) Monday, so we haven’t made any decisions about that,” Counsell said. “I don’t think we have to make a decision until the off day (on Thursday).”