With the Cubs in the middle of a playoff push, their pitching rotation has taken a big hit.

Right-hander Marcus Stroman was diagnosed with a right rib cage cartilage fracture and does not have a timetable yet to return, the team told reporters Wednesday.

The former Met was already on the 15-day injured list with right hip inflammation and was working back toward making a start against the crosstown rival White Sox, but experienced pain in his right side while throwing a bullpen session Sunday, according to the Associated Press.

Cubs president Jed Hoyer did not have any information regarding a potential return for Stroman.

“I have no idea. That’s the honest truth,” Hoyer told reporters Wednesday, according to ESPN. “We don’t really know at this point. Obviously, we’ll give him a real rest period and see how he feels.

“It’s an unusual injury for a pitcher. We found out on Sunday he was having some issues. We didn’t know if it was muscular, we didn’t know if it was skeletal. We didn’t know if it was indigestion. We didn’t know what it was.”

The 32-year-old right-hander got off to a hot start in the first half for the Cubs, winning nine games with a 2.96 ERA and 96 strikeouts and was named a National League All-Star.

But in a small second-half sample, Stroman struggled before hitting the shelf, allowing 18 earned runs over 16 innings.

As a team, though, the Cubs have surpassed many prognosticators’ projections and are in the thick of the NL wild-card race, a game back of the final playoff spot coming into Wednesday.

They even added infielder Jeimer Candelario and reliever Jose Cuas at the trade deadline and their playoff odds now sit near 50 percent, according to Fangraphs.

But losing Stroman, whom the Cubs signed away from the Mets to the tune of a three-year $71 million deal before the 2022 season, could put a crimp in those plans.