JUPITER, Fla. -- Sonny Gray said he knows from experience just how frustrating hamstring injuries can be for pitchers -- regardless of how mild or severe they are -- after having gone through two such issues in 2022 while with the Twins.

Ironically, Gray said those prior injuries likely kept him from suffering a much worse hamstring strain on Monday, and potentially missing more time in the season ahead for the Cardinals.

Gray, the centerpiece of the Cardinals pitching makeover from the offseason, breathed a sigh of relief on Tuesday after an MRI revealed only a “mild strain” in his right hamstring. Gray breezed through 1 2/3 innings of scoreless work against the Nationals on Monday before feeling tightness in his right hamstring. Experience taught him to stop right there instead of trying to push through the pain in his first season with the Cardinals.

"I remember doing this in 2022 when I was making a start in Boston. Same thing -- I threw one pitch and felt a little grab in a very similar spot,” Gray said. “In that one, I threw a couple more pitches and made it through and I was like, 'I can't do this anymore.'

"I think maybe that [2022 injury] was the initial [reason he stopped on Monday]. I was like, 'Crap, I've felt this before and I probably should stop now.' I think I was back in a big league game in 21 days. ... Not to say I'll be back in 21 days, but it is somewhat of a similar feeling. Physically, I feel like I am in a much better spot now than I was then [in 2022], which is a good thing.”

Gray, the runner-up for the American League Cy Young award last year, was scheduled to be the Cardinals’ Opening Day starter on March 28 against the Dodgers. President of baseball operations John Mozeliak said on Tuesday that Gray doing so would “probably be challenging,” considering the time that he could miss during Spring Training. Mozeliak said Gray’s injury isn’t so severe that the team will explore adding pitchers via free agency or trades.

“I’ve experienced a lot of key pitchers going down in Spring Training in my career, and it’s always frustrating because a lot of your offseason planning is what you want it to look like for 162 [games], and now you’re having to deviate from that,” Mozeliak said. “It’s a bummer, but it could have been worse. So, I think you approach today with a little more optimism than maybe if it was more dramatic [injury-wise].”

If Gray can’t go on Opening Day, the Cardinals could turn to one of the other four veteran starters on their staff, manager Oliver Marmol said. In addition to adding Gray, the club signed Lance Lynn and Kyle Gibson to pair with incumbent starters Miles Mikolas and Steven Matz. Matthew Liberatore or Zack Thompson, who are competing for a possible sixth spot in the rotation, would slide into Gray’s spot if his injury lingers into the season.

"When you think of Opening Day, it's a matter of somebody who's not going to scare," Marmol said. "There's a lot going on on Opening Day. It's different than any other start, and we have guys who will handle that just fine."

Making his second spring start on Monday in West Palm Beach, Gray breezed through 1 2/3 innings before motioning catcher Willson Contreras to the mound mid-at-bat. Soon after, Marmol, trainer Adam Olsen and pitching coach Dusty Blake followed, and Gray was out of the game.

Looking back on it, Gray thinks stopping when he did led to him feeling much better than expected on Tuesday when he woke up. While he can’t put a firm timetable on when he might be able to return, Gray was encouraged with the physical activity he was able to do before the Cardinals took on the Twins.

"I think a determining factor is that today I woke up and I didn't feel worse,” said Gray, who made 32 starts in an injury-free 2023 season with the Twins. “It felt a little better than they probably expected. … I woke and hopped on a [stationary] bike, and we're already doing strengthening [exercises].

“For me, within the next two, three, five days -- it's about making as much improvement as I can. Today it's a good day and a good feeling. Then, to make as drastic improvements as possible [in the coming days] is going to be good. I don't know, but tomorrow I need to have a good day."