FORT MYERS, Fla. -- When the Red Sox signed righty Lucas Giolito as their key free agent in the offseason, the hope was that he would lead the team in innings while being one of the best comeback stories in MLB.

The optimism that surrounded Giolito’s acquisition in December has been put into serious jeopardy, with Red Sox manager Alex Cora announcing on Tuesday that the 29-year-old is dealing with discomfort in his right elbow.

It is all but certain Giolito will open the season on the injured list and miss a significant amount of time beyond that.

It was clear from the way Cora, chief baseball officer Craig Breslow and Giolito spoke that nobody is viewing this as a short-term injury.

“Yeah, extremely disappointing,” said Giolito. “I've always prided myself on posting, staying healthy. You know, I've done everything in my power to do so. I haven't dealt with a serious injury in a very long time, so [it] definitely sucks a lot.”

While Giolito has already had an MRI, the Red Sox are still in the process of evaluating the results of a battery of tests he’s undergone from the team’s medical staff.

“I think anytime you go through this process, I think it's wise to be tempered a bit,” said Breslow. “You know, my sense is this is a real injury. Beyond that, I don't think it makes a ton of sense to speculate and certainly don't want to create any expectations that are unfair or unreasonable.”

Giolito said he felt the discomfort in his elbow while making his most recent Grapefruit League start on March 1 against the Twins. In that outing, Giolito didn’t look like himself, giving up two hits, four runs and three walks while throwing 48 pitches in 2 1/3 innings.

Cora said the Red Sox will have another update on Giolito by the end of the week.

“Obviously we're concerned about it. Obviously, he's gonna miss some time,” said Cora. “How long, we don't know yet. We're in the process of still gathering information but obviously, not a good day for us.”

ESPN's Jeff Passan reported Tuesday morning that initial tests showed Giolito "likely has a partially torn UCL and flexor strain," which could put his 2024 season in doubt.

The Red Sox didn’t confirm or deny the report, just saying repeatedly they are still in the information-gathering phase. It’s possible Giolito will seek a second opinion.

“Yeah, we're still kind of putting the pieces together pretty much in real time,” said Breslow. “Can certainly say that he had discomfort in his last start. Medical is working through their process. And I think we're still trying to put all the pieces together and gather the information.”

While the Red Sox are being methodical in their approach to make sure they come up with the right course of action, Giolito was clearly dejected. He had come in with big hopes of bouncing back from a couple of down seasons and getting back to the upper-echelon starter he was from 2019-21.

Now, he just wants to be able to pitch.

“It's pretty unfortunate,” Giolito said. “I’m choosing my words carefully. I don't want to be swearing and stuff, but yeah, it's obviously not fun to deal with.”

The loss of Giolito for any length of time is significant, considering the rotation was probably the biggest question mark on the team even with him.

Could the Red Sox get more aggressive on an external addition still on the free-agent market such as Jordan Montgomery, who the club has been loosely linked to for weeks? Or will they double down on their goal of having their mid-20s pitchers take the next step in their careers?

“I think over the last couple of weeks, it's become evident that there are a number of guys that we have in camp that appear ready to take a step forward,” said Breslow. “And I think that's a credit to the work that they've done and a credit to the pitching infrastructure and the work that [pitching coach Andrew Bailey’s] done. We've also maintained that if there was an opportunity to improve the team through some external acquisition that we needed to be responsible in trying to track that down as well. So I think that's where we currently are.”

Nick Pivetta would be the lone veteran in the rotation that doesn’t include Giolito. The Red Sox are counting on their mid-20s core of pitchers (Brayan Bello, Kutter Crawford, Garrett Whitlock, Tanner Houck and Josh Winckowski) to take a collective step forward this season. Cooper Criswell, a swingman the Sox signed to a one-year contract in the offseason, is another pitcher the team is stretching out.

“I think this is tough for us and tough for Lucas,” said Breslow. “He's a guy that has taken a lot of pride in his ability to post and that was certainly something that was attractive to us. Obviously, don't want to kind of speak until we know exactly what we're dealing with. But I know he's frustrated, wants to take the ball on Opening Day, so we'll evaluate where we are and figure out what the best path forward is.”