Cubs ace Shota Imanaga was placed on the 15-day IL Monday afternoon with a left hamstring strain.

The extent of the injury became more clear when manager Craig Counsell spoke to reporters after the Cubs’ 9-2 win against the Giants at Wrigley Field.

“The MRI showed he’s got a hamstring strain,” Counsell said postgame. “He’s presenting to the doctor with a very mild hamstring strain. That makes us optimistic. I think it’s probable we’re gonna be past two weeks here because we’re gonna be cautious and make sure that he’s back to 100%. But all in all, pretty good news.”

Imanaga injured his hamstring on Sunday afternoon in Milwaukee as he went to cover first base in hopes of completing a double play.

On his way to the bag, Imanaga began to clutch the back of his left leg in visible discomfort. Counsell, along with athletic trainer Nick Frangella and interpreter Edwin Stanberry, immediately went out to check on Imanaga. He was pulled from the game without throwing another pitch.

The left-hander missing any time this season is not ideal – especially after co-ace Justin Steele went down with season-ending flexor tendon surgery. However, the Cubs hope to have Imanaga back in the rotation some time in the near future.

Cubs president of baseball operations Jed Hoyer spoke pregame and addressed how Imanaga’s spot in the rotation will be filled.

[In wake of Shota Imanaga injury, what comes next for Cubs pitching staff?]

“I mean, no one’s going to be Shota,” Hoyer said. “We have to have guys step up. Our depth is getting challenged a little bit. I think we still have pretty good depth and options, and we’ll have to have those guys step up.”

One pitcher in particular who has stepped up in Steele’s absence has been Colin Rea. In four starts this season, Rea has posted a 1.86 ERA, allowing two earned runs or fewer in each of his four starts.

“I think Colin’s done a great job stepping up since Steele went out, and obviously guys will have to step up with Shota out,” Hoyer told reporters.

The Cubs rotation is currently filled with Matthew Boyd, Jameson Taillon, Colin Rea and Ben Brown. Cubs top pitching prospect Cade Horton is another potential option to fill Imanaga’s spot in the rotation.