FORT MYERS, Fla. -- The excitement of being back on the mound without any concerns about his health was short-lived for Red Sox left-hander James Paxton, who left his Grapefruit League debut on Friday with a right hamstring injury, the extent of which is unknown at this point.

Making the latest health mishap more frustrating for Paxton is that he looked like his vintage self for most of his 1 2/3 innings in Boston's 9-4 win over Minnesota, retiring all five batters he faced and getting one strikeout.

“We’ll know tomorrow,” said Red Sox manager Alex Cora. “Obviously, not perfect. Hopefully it was just a cramp. I think obviously with him, we’ve got to be very careful. It's a shame because he was throwing the [heck] out of the ball today. His location was great, velo was up. ... And that happened. Hopefully it’s nothing and we can just continue to move on.”

Paxton first felt the discomfort on his second-to-last pitch. On his next offering, he got Michael A. Taylor on a flyout to left and could be seen stretching out trying to get loose. After a quick visit with the training staff, Red Sox manager Alex Cora wasted no time taking Paxton out. He was only scheduled to get one more out.

“My hamstring just grabbed on me a little bit just as I was kind of starting to find that firing pin to let the ball go a little bit harder,” Paxton said. “I wanted to step on it a little bit and the hamstring just grabbed. We'll see what we got. We don't really know yet. But we’ll see how I come in feeling tomorrow and go from there.”

Considering how comfortable the 34-year-old Paxton felt throwing before the injury, the day was a mixed bag. In a 19-pitch outing in which Paxton threw 12 strikes, his fastball topped out at 94.7 mph, per Statcast.

“I think there's positives and negatives,” Paxton said. “I think that going out there and filling up the zone like I did felt good. Some good breaking balls, fastball felt pretty good. I felt like it was coming out of the hand well. But then this happens and now we're gonna have to deal with this so that I can continue moving forward. I'll do whatever I have to do to get back out there.”

It was too soon for Boston’s training staff to know the severity of the injury.

“They said it cramped up a little bit. Not sure if it’s a strain yet,” said Paxton. “See how it goes here. It might just be a really light strain, they said my strength was still pretty good.”

Paxton is one of seven starters vying for five spots in Boston’s rotation. However, with Garrett Whitlock being brought along at a conservative pace as he comes off right hip surgery, and Brayan Bello suffering right forearm tightness earlier in camp, Paxton looked like he was a healthy spring away from being on the Opening Day roster. Now, he is back in limbo.

Earlier this week, Cora said that Paxton had been the player who had caught his eye the most in Spring Training.

Dating back to the beginning of the 2020 season, Paxton has logged just 21 2/3 innings. His ‘21 season was limited to just one start, after which he had Tommy John surgery.

Paxton signed with Boston in December 2021, and spent most of the ‘22 season rehabbing from surgery. The hope was that Paxton would pitch late in the season for Boston, but in his first Minor League rehab start he suffered a Grade 2 left lat strain.

Everything this spring had gone perfectly until Friday.

“This is not how I wanted this to go,” said Paxton. “I wanted to go through Spring Training clean. But, you know, I can't control that. All I can control is going to work on this now and doing whatever I can to get back out there and pitch again.”