The Chicago Cubs’ rotation took a hit that will have a ripple effect in a crucial season.

Justin Steele will undergo flexor tendon surgery on his injured left elbow and miss the rest of the year, Cubs manager Craig Counsell told reporters in Los Angeles on Sunday.

Steele was placed on the 15-day injured list Wednesday with elbow tendinitis. It’s a devastating blow to the Cubs, who had raced out to a 10-7 record amidst a brutally difficult March/April schedule.

The top of the rotation was supposed to be a Cubs strength this season with Steele and Shota Imanaga headlining it. Now, they’ll have to find a way to replace his presence.

Steele, a 2014 Cubs fifth-round draft pick, had Tommy John surgery on his left elbow in 2017 when he was a minor leaguer. He recovered and eventually developed into a success story for the Cubs’ pitching infrastructure, which was a question mark for long periods under the Theo Epstein/Jed Hoyer regime.

Steele rose through the minor league ladder to debut in the big leagues in 2021, as he posted a 4.26 ERA in 20 games (nine starts) and 57 innings. Steele was in the Cubs’ rotation in 2022 and showed what he could do, posting a 3.18 ERA in 24 starts, although a back injury cost him the final month of the year.

Steele’s real breakthrough campaign came in 2024, when he was 16-5 with a 3.06 ERA in 173.1 innings, earning his first All-Star Game selection and finishing fifth in National League Cy Young voting. He did miss time that season with a forearm injury.

A fluke hamstring injury on Opening Day in 2024 caused Steele to miss most of April, and then elbow tendinitis in September sidelined him for a little over two weeks. He said Wednesday that the injury he felt was like the one last season.

“I would say I’m leaning that way,” Steele said. “I was coming in yesterday, prepared to go about the normal rotation, standard in-between-start stuff. N​​ow we’ll just be able to figure out exactly what it is and attack it.”

But he underwent an MRI on Thursday, and he and the Cubs decided to seek another opinion to get to the bottom of it.

“Obviously had the MRI — we’re going to get some more opinions on it,” Counsell told reporters before the opener of the three-game series against the Dodgers on Friday. “We’re kind of dealing with the same thing we dealt with last year. For that reason, I think Justin wants to make sure and we want to make sure we get the right information moving forward.

“So, he’s going to get another opinion, and then we’ll go from there.”

That led to Sunday’s crushing news.

Steele had turned in his best start of the young season Monday against the Texas Rangers, tossing seven shutout innings with eight strikeouts and allowing just three hits and two walks. That’s the level of performance he brought to the Cubs’ pitching staff.

In the interim, it seems likely that Colin Rea will slot into the rotation. He was signed to a one-year deal this offseason to provide rotation depth, and he started the season in the bullpen. He has pitched 5.1 scoreless innings this season, and is starting Sunday’s series finale against the Dodgers.

Javier Assad, who started spring training with an oblique strain, is making a rehab outing with the Triple-A Iowa Cubs on Tuesday, and could be back by the end of the month. Jordan Wicks pitched three innings Sunday for the I-Cubs and is another depth option if needed.