The Kansas City Royals entered spring training with a deep stable of starting pitchers.

That depth will soon be tested.

Royals right-handed pitcher Stephen Kolek has a strained left oblique. He was set to pitch in Wednesday’s Cactus League game against the Seattle Mariners but was pulled back while warming up in the bullpen.

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The Royals will take a cautious approach on Kolek’s health. Acquired from the San Diego Padres last season, he will undergo further evaluation in coming days.

“We are going to get an image later today just to see what the severity of it is,” Royals manager Matt Quatraro told reporters in Surprise, Arizona. “We are obviously hopeful that it’s not too serious.”

Kolek is competing for a spot in the starting rotation. Noah Cameron, Ryan Bergert, Luinder Avila and Bailey Falter are also vying for the role. Cameron is expected to get first crack at the job, but Kolek remains in the Royals’ plans.

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They want to keep him built up as a starter and he pitched well last season. He posted a 1.91 ERA in five starts with the Royals.

The Royals love his competitiveness on the mound and effective control — he recorded 21 strikeouts and just five walks for KC in 2025 — as well as his ability to limit runs.

“Getting that depth there was really starting to help us into this year,” Royals pitching coach Brian Sweeney said. “So it’s going to be really important. It’s really difficult to take 13 pitchers and go through a major-league season. So to have that depth is extremely important to us.”

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Earlier this spring, Kolek mentioned the importance of staying healthy. He noted that he’d had a great offseason in preparation for the upcoming season, refining his pitching arsenal and focusing on throwing his four-seam fastball more often.

Kolek hopes to return to game action soon. In the meantime, the Royals will allow him to get healthy and resume his ramp-up toward the regular season. It’s expected that he will be shut down for 5-7 days, although his absence could extend longer pending what’s found in further evaluation.

He had been tabbed to pitch two to three innings Wednesday.

“The shutdown will affect that and (his ability) to get back into games,” Quatraro said. “We will see how quickly that happens.”