The Cardinals have tried to avoid it with caution and patience, but Miles Mikolas will not be ready for the start of the 2021 season.

The right-hander, who had long been slated to throw a bullpen session on Wednesday, will not do so anymore, manager Mike Shildt said after Tuesday’s 5-3 Grapefruit League loss to the Mets. Instead, Mikolas will have some imaging done on his right shoulder to try to pinpoint the cause of the soreness that has plagued him throughout camp.

“That will impact his beginning of the season, clearly,” Shildt said. “We’re hopeful that it’s a little bit of a blip and just a little bit longer recovery than anybody hoped.”

Mikolas is coming off July surgery to repair the flexor tendon in his right forearm, a procedure that kept him out of the shortened 2020 season. He reported to camp feeling good, throwing side sessions and taking part in live batting practice on Feb. 25. He has not faced live batters since.

The initial thought was to have Mikolas throw his side session this past weekend, but those plans were pushed back to Wednesday to give him extra time to recover from some of the soreness. Now it’s unclear when Mikolas will throw from a mound again, though Shildt has said he’s participated in “aggressive” catches over the past week.

“We’re hopeful that it’s not anything overly serious,” Shildt said. “We don’t want to push, but also want to do a little bit more due diligence and look at it a bit more closely.

“We haven’t pushed him to this point, we’re not going to push any of our guys. Miles is frustrated, we’re frustrated for him.”

Doubts of Mikolas’ readiness for Opening Day started to swell when president of baseball operations John Mozeliak described his timeline as “urgent” on Sunday.

Questions now turn to how the Cards will replace Mikolas at the outset of the season. St. Louis is fortunate in that it operates with four off-days in the first month of the season, allowing the club to potentially employ creative rotations. Even still, the rest of the rotation faces questions, with the fifth starter still not solidified (even before Mikolas was sidelined), all but two starters unable to complete the first inning of Grapefruit League action and candidates like Alex Reyes formally removed from the rotation competition and pinned to bullpen roles.

Through it all, the Cardinals remain full of confidence in their depth. Mikolas’ setback is just another test of that faith.