Corey Rosier, one of the two prospects who the Red Sox acquired from San Diego in the Eric Hosmer trade at last year’s deadline, began meditating, read more and changed his diet during a productive offseason.

“I actually experimented with intermittent fasting this offseason,” Rosier said by phone Tuesday. “It led me to being the heaviest but also the most lean I’ve ever been. So it really worked for me. I wouldn’t break my fast until 11:30, 12 o’clock every day. So I’d work out and hit and train on an empty stomach. And there’s a lot of science proving it actually helps with muscle growth and I noticed a difference.”

Rosier, a 5-foot-10, 190-pound outfielder with speed, has enjoyed a nice start to the 2023 season. The 23-year-old left-handed hitter is 15-for-42 (.357 batting average) with a .400 on-base percentage, .452 slugging percentage, .852 OPS and four doubles in 14 games for Double-A Portland. He has been successful in 9-of-10 stolen base attempts. His nine steals are tied for second most in the organization.

“I put in the work this offseason, so everything is coming full circle,” he said.

The Red Sox added speed in the Hosmer trade, which sent pitching prospect Jay Groome to the Padres. High-A Greenville’s Max Ferguson, who Boston acquired along with Rosier and Hosmer, also has nine steals so far.

Rosier would wake up at 6 a.m. and start lifting at 7 a.m. each morning. He finished his gym workouts around 8-8:30 a.m., then hit. He worked on his hitting until about 10:30 a.m.-11 a.m. What did he eat when the clock finally struck noon?

“I’m a big breakfast guy,” Rosier said. “I would always go with eggs. Usually about four. And then an everything bagel and some bacon with that too. That was the go-to.”

He said reading more and meditating was “to try to strengthen the mind.”

“I got into reading and also meditation and different things like that because I feel the mental side is so big and a lot of people don’t pay enough attention to it,” he said.

He read Kobe Bryant’s “The Mamba Mentality: How I Play” as well as some science fiction books.

He also focused on his bat path during the offseason after the Red Sox pointed out that his path sometimes got too steep.

“So this offseason, I really went to work on getting stronger with my top hand to keep that direction good,” he said. “It’s really paid off. Getting bigger, faster, stronger, that’s always the No. 1 thing people talk about. But I would say that the biggest thing is bat path and keeping the direction.”

Speed is a big part of Rosier’s game. He went 40-for-45 in steals last season. He has 62 steals in 154 minor league games.

“I think it’s really something that can change the course of the game being able to take that extra (60 feet, six inches),” Rosier said. “So every time I get on, I’m looking to run if the situation calls for it.

“I hate making outs so if I chop a ball, I’m gonna give it everything I’ve got every time to try to steal that knock,” Rosier added. “I think at the end of the year, once you look back and realize how many times you’ve done it, it really starts to add up. It doesn’t always show in the stat lines but it’s definitely apparent. And even showing a bunt from time to time, keeping the defense honest. It opens up more holes for me and allows me to get a few more base hits in there because they have to play to protect for the bunt.”

Rosier has a .383 on-base percentage in 654 minor league plate appearances.

“I’d say I’m a gap to gap guy,” Rosier said. “I definitely have home run power but that’s never going to be my game to try to hit home runs. I’m going to make my money blistering balls in the gap and running, using my speed.”

Rosier can play all three outfield positions.

“I’ve spent time in all three,” he said. “And honestly just anyway to stay in the lineup. Having that versatility and being able to play all three and not be limited I think is huge. I think it will keep me in some lineups, keep me around for a while.”

He has been working on his first step.

“Me and our outfield coach here, we were talking about my first step,” he said. “Sometimes I don’t time it up quite right and I’ll kind of have to restart, which with my speed, I still get away with sometimes. But there’s some balls I can maybe get to where I may not get there if I don’t have that good first step. So I’ve really been locking in on getting that timing down and it’s almost like I’m being shot out of a cannon. I can basically see where the ball’s going before it’s even hit off the bat.”