FORT MYERS, Fla. -- Brayan Bello went back to the School of Pedro (Martinez) this offseason, and the result is a new-and-improved slider that could lead to a significant step forward for the talented righty in 2024.

For Bello to have the opportunity to go pitch off the mound at Martinez’s property in the Dominican Republic and get tips from a living legend is, well, invaluable.

The 24-year-old Bello, perhaps the most talented member of Boston’s young starting rotation, felt instant improvement after Martinez’s tutelage.

“I was able to work out with him three or four times [in the winter],” said Bello. “When I got there, my slider wasn't in the best shape. So he gave me a few tips. And that same day, I was able to get a good grip on it. I was throwing it consistently and then in the next few days, I was gaining more confidence with it. So yeah, it was a very good time that I spent with him and with Pedro and helping me to get my slider sharp.”

Bello feels the slider can be his key third pitch behind his filthy sinker and plus-changeup. He also has a four-seamer that he plans on throwing out of the strike zone to get some chase.

On Thursday, Bello threw live batting practice on the main mound at JetBlue Park and felt in a pretty good groove. And the slider was playing.

“I felt more comfortable with that pitch,” Bello said. “I feel like I can throw it in any count. Today in live BP, I used it and felt really good about it. So it was a good offseason for that pitch. I feel like my confidence is up with that pitch.”

The other reason Bello could be positioned to take the “leap” in 2024? An improved physique Bello knew he needed when he wore down a bit at the end of his first full Major League season.

“Yeah, I was working on my lower body, my back as well,” Bello said. “At the end of last year, I felt a little bit weak. So I wanted to strengthen my lower body so I can get more innings and feel stronger at the end of the year.”

Though 2023 was generally a success for Bello, he hit a wall at the end, giving up a total of 13 runs over nine innings in his last two starts.

In fact, he lost his last three starts, bringing his overall record to 12-11 while his ERA swelled from 3.68 to 4.24.

“I had a few outings at the end of the year that weren’t the best,” Bello said. “So for me, I needed to tackle that right away and I wanted to tackle that right away being aggressive from the first day [of the offseason]. But yeah, I was kind of disappointed by the last few starts last year.”

What is Bello looking to accomplish this season?

“Try to apply everything that I learned last year and all the experiences that I had last year,” Bello said. “I’ve been doing it in the bullpens, and that’s something that helped me a little bit, but also, just trying to get better in all areas that I can.”

There’s a chance Bello will start Opening Day on March 28 in Seattle, but that competition is ongoing. At the very least, he will be a starter the Red Sox will be counting on heavily.

The Red Sox are evaluating Bello in a different way this spring than a year ago, when he was just trying to win a spot in the rotation.

“He's getting ready for the season,” said Red Sox manager Alex Cora. “It's a lot different than last year. I think physically, he's way ahead. I think he learned that in the offseason [last year] … it's not that he took it for granted, but he was very specific this offseason the things he needed to work on, especially body-wise. You see him around. He's grown into a man now. He's gained some weight, he looks stronger, he did an outstanding job in the offseason. Now, it's about his buildup and being ready for the opening series.”