JUPITER, Fla. -- The soreness that Miles Mikolas pitched through last season reappeared in the first week of spring and could delay his appearance in Grapefruit League games.

Mikolas did not throw his scheduled bullpen Saturday after experiencing the soreness in his right flexor tendon and subsequently was put on a no-throwing program for the next several days, at least.

The Cardinals starter had a platelet-rich plasma (PRP) injection at the end of last season to address the problem, and he had an MRI then, too, to make sure there wasn’t ligament damage. Mikolas had another MRI on Saturday morning, and nothing worse was found. Tendons are tissues that connect muscles to bones, and the flexor tendons connect the muscles of the forearm to the bones in the fingers and thumb.

The Cardinals will see how Mikolas feels Sunday before determining whether a second PRP treatment will be used. There’s no timetable yet on when he might be able to return to throwing. He felt the soreness again after his bullpen session Thursday.

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“Me being the kind of guy I am, probably tried to ramp it up a little too quick,” Mikolas said. “I had a nice easy throwing program this winter, and I felt really good, and then camp starts and you just kind of get real excited. You want to get going. I got a little bit too eager I think, just trying to cut it loose too early. Just take a little breather, take a step back and go from there.”

Cardinals manager Mike Shildt said it was too early to say whether this will delay Mikolas to start the season. Mikolas said it’s “very possible” that he’ll be able to get enough work in to start the season on time.

“Once it feels good, I can get going pretty quick,” Mikolas said. “My body is in good shape. I’ve already been off a mound, so it’s not like I need to necessarily build up that strength to get all the way up off a mound, it just needs to feel a little bit better.

“No one wants to go into the season limping. That also being said, you don’t want to go into the season not feeling your best. And it’s real cliché, but you’d rather miss a week at the beginning of the season than a week at the end of the season when things get exciting. So all that stuff to take into consideration.”

Mikolas described how the rest over the offseason helped the tendon heal, and the new tissue there could be sore because it has to adjust to the intensity of throwing a baseball.

“So it just needs to adjust, it needs time to go, ‘Oh, this is throwing a baseball? This is pretty tough,’" Mikolas said. "So now it just needs a couple of days to strengthen up, get its R&R, its TLC and then come back strong.”

Shildt said multiple times Saturday that Mikolas’ injury is not related to his UCL, and the Cardinals are encouraged by the scans that showed the stability of Mikolas’ elbow. Shildt called the injury a “minor setback,” while Mikolas emphasized that there’s comfort knowing that he was able to pitch through it last season and that it healed with rest.

“I’m not as concerned because it’s more tendon,” Shildt said. “We can heal that quicker. Ligaments don’t typically repair. I’m concerned he’s set back, I’m not concerned that it’s a major setback relative to what could be significant time based on a ligament or anything. Nothing is showing in the imaging that it’s worsened, it just hasn’t healed to the way we would like it to heal where it’s going away.”

The Cardinals have the starting-pitching depth to cover innings this spring and into the season, too. Carlos Martinez is on a starter’s schedule and is competing with Kwang-Hyun Kim, the Korean lefty signed this winter, for a rotation spot. The Cardinals are hoping that Martínez’s shoulder, where he’s had issues in the past, can handle a starter’s regimen this season. Daniel Ponce de Leon, Austin Gomber and John Gant are also candidates for a spot this summer, too.