Action in the Red Sox/Pittsburgh Pirates game Monday at JetBlue Park. CJ HADDAD

While the Boston Red Sox picked up a win Monday afternoon at JetBlue Park, a looming loss reared its head following the game via news from manager Alex Cora.

It was confirmed Boston’s biggest starting rotation pick up, Lucas Giolito, will require elbow surgery, with the procedure taking place Tuesday in Birmingham, Alabama.

“The extent of it, we don’t know yet,” Cora said of what kind of procedure the right-hander will undergo. “We know it’s with the ligament. So we’ll know more (Tuesday) when they go in. The type of surgery, we don’t know yet.”

Giolito, an All-Star in 2019 with the White Sox, felt discomfort during a Spring Training start on March 1. There had been heavy speculation since he was removed from that game on his future for the season, which is now certainly one that will be missed.

On a brighter note, a candidate to break camp in the starting rotation, Cooper Criswell, was as solid as can be against the Pirates Monday, not allowing a run over 3 2/3 innings, giving up two hits, no walks and striking out four.

“I felt like this was the best (outing) of the spring so far,” Criswell said. “It’s just continuing to stack days and go from today.

“It’s nice to know I’m in the mix (for a rotation spot), but I think we’ve got a great group of guys here. At the end of the day, we all want to win games. (Cora, Chief Baseball Officer Craig Breslow,) everyone knows I’m willing to do whatever they ask of me, whether that is to start, come out of the pen long relief or even just a one-inning role, I’m pretty much open to whatever. At the end of the day I think everyone here just wants to win baseball games.”

The 6-foot-6 Criswell was a 13th round pick of the Los Angeles Angles in the 2018 MLB Draft and made his major league debut in 2021.

In 2022, he was claimed off waivers by the Tampa Bay Rays and made 10 relief appearances for the club in 2023, pitching at least two innings in each game.

He was designated for assignment by the Rays in Nov. of ’23, and signed with the Red Sox as a free agent on Dec. 13.

While he doesn’t light up the radar gun (average fastball 88 mph in ’23), Criswell features a handful of pitches with movement, including a slider/ sinker, cutter and change-up.

“I feel like guys like me know their role, and they try and go out there and execute that role to the best of their ability,” Criswell said on his lack of velocity, which the Sox have been trying to improve this camp. “I just use what I have to try and do the best I can and get out there and get quick outs, soft contact.”

Cora said “it’d be great” if the 27-year-old could see an uptick in velocity, but that he does a good job of moving the ball around the strike zone.

“We’re very pleased with the progress of where he’s at,” Cora said “It’s a different angle. The radar gun does show 97, 98, but there’s pitchability, and there’s value in that.

“Not everybody can overpower people and live in that vertical area. You still have to make pitches.”

Red Sox top prospect Marcelo Mayer made his Spring Training debut Monday in relief at shortstop. While he did make an error in the field, the 21-year-old and ’21 first-round pick (4th overall) ripped a double in his lone at-bat.

“I’m very impressed with, and this is from the past, too, how calm he is in the batter’s box,” Cora said. “He’s a good player. He understands the game. The double play we turned with (Nick Sogard) was great. The release — he reminds me a lot of Carlos (Correa). Straight over the top with something behind it.”

A veteran newcomer to the club, C.J. Cron, also made his spring debut Monday after signing a 1-year minor league deal with the Sox on March 1. The right-handed slugging first baseman is coming off a season where he dealt with nagging back injuries, limiting his time on the field between the Rockies and Angels.

Cora and the club feel Cron could be a valuable bat off the bench, especially facing left-handed pitching.

“Felt good,” Cron said following his work over four innings, going 0-for-2 at the plate. “Obviously the results aren’t great, but it’s alright, we’ve got a lot of time left. It felt great to get out there with the team and get some (at-bats) under my belt.”

Cron was an All-Star with Colorado just two years ago, posting career highs in home runs and RBI. With his health now trending in the right direction, Cron hopes to be a contributor.

“I think we have a really good plan in place here,” Cron said. “The training staff is making it a priority that we do things a little bit differently in the weight room, in the training room, and hopefully that’s the main thing is keeping it under control.”

Red Sox fans can get a close look at the future of the club this weekend, as the MLB Spring Breakout Series comes to JetBlue Park this Saturday afternoon as they take on the Braves. Both lineups will feature top prospects in the organization.