When the Cubs placed Julian Merryweather on the 15-day injured list Sunday less than an hour before game time, the move came as a bit of a surprise.

Merryweather had just shut down the Dodgers on Friday, getting 4 outs to pick up his first hold of the season.

On Sunday afternoon, the Cubs placed him on the IL with a right shoulder injury and recalled Daniel Palencia. The initial thought was the Cubs hoped Merryweather would not be out long but on Monday, they received clarity on the injury.

After undergoing imaging, Merryweather was diagnosed with a stress fracture in a rib in his back and will be shut down from throwing for 4 weeks. Including the ramp-up period after that to get ready for big-league games, Merryweather will likely be out until at least June in a best-case scenario.

“It’s a unique pitching injury, for sure,” manager Craig Counsell told reporters before Monday’s game in San Diego.

Merryweather reported feeling the issue in his shoulder/back after one of his final pitches in Friday’s outing. Neither he nor the team thought much of it initially but the concern grew as he reported feeling sore on both Saturday and Sunday.

“Candidly, we were hoping it’d be a little shorter stay on the IL but that’s the breaks,” Jed Hoyer told reporters in San Diego Monday. “We’ll take about 4 weeks, let it heal and re-image it and see how it is.

“But yeah, I think it was probably a little worse diagnosis than we had imagined. And it was tough to get through it.”

Merryweather enjoyed a breakout season last year with the Cubs. They claimed him on waivers in January after he spent time with Toronto, where he flashed potential but injuries derailed his career.

With the Cubs last year, the 32-year-old right-hander made a career-high 69 appearances with a 3.38 ERA, 17 holds and 2 saves. He also struck out a whopping 98 batters in 72 innings.

Merryweather filled an important role in the back end of the Cubs bullpen, teaming up with Mark Leiter Jr. and Héctor Neris to set the table for closer Adbert Alzolay.

Now the Cubs will be without one of their best relievers for the next couple of months, in all likelihood.

On Monday night in San Diego, the Cubs bullpen gave up 7 runs (5 earned) as the team let an 8-0 lead slip away.

“People have to step up,” Hoyer said before Monday’s game. “I think what [Merryweather] does incredibly well is he’s platoon-neutral. You can kind of give him an inning and you don’t have to worry about what pocket it is.

“And I think that’s the hardest part is that other guys are probably a little bit more pocket-oriented and platoon-oriented. And he gives us a guy that’s neutral and that’s really, really beneficial.”

In Merryweather’s spot in the bullpen, Palencia came up big Sunday after the rain delay, covering the final 3 innings to pick up the first save of his young career.

“He saved us, honestly,” Hoyer said. “That was really big, getting those 3 innings. He threw strikes, attacked guys and that’s what the situation called for.

“He’s going to help us this year for sure. I think there’s probably a lot of guys we’re gonna have to rotate through that part of the bullpen and I think he’s gonna be one of them that has to have an impact.”