LAKELAND, Fla. -- The second pitch of Michael Fulmer’s live batting practice session against hitters Wednesday morning sent Willi Castro swinging so hard that he fell over as he missed, leaving both of them laughing as Tigers teammates reacted.

It was an offspeed pitch as Castro went hunting for Fulmer’s fastball. It was a reminder how nasty Fulmer can be when he has his pitch selection working and how difficult he can be in small, adrenaline-filled doses.

“It felt good throwing that,” he joked afterward.

Not bad for his first session against hitters since last season ended. It’s cold back home in Oklahoma, Fulmer pointed out, and nobody wants to go outside and swing a bat against him.

On this same date a year ago, Fulmer was in camp competing with Casey Mize and Tarik Skubal for a spot in Detroit’s rotation. He was searching for his power fastball, struggling to throw strikes and taking out his frustrations in the weight room after a particularly rough outing. The notion that he would be able to get back in his groove in his second season back from Tommy John surgery was in serious question.

He looked like a pitcher at a crossroads. Then manager A.J. Hinch and pitching coach Chris Fetter proposed using him in the bullpen.

It was arguably a turning point for both pitcher and manager. For Fulmer, the bullpen was his avenue to regaining some of the electric stuff that earned him AL Rookie of the Year honors in 2016, even if he only gets to throw in smaller doses.

For Hinch, getting Fulmer to buy in on a bullpen move for the good of the team was one of several major steps early in setting the culture he wanted with support from the veterans he inherited.

“The buy-in from the players is the number one thing that you need in order to maximize any move,” Hinch said. “Buy-in helps get better faster. And when the veteran guys do it, the young guys follow suit.”

As the Tigers begin Spring Training in need of rotation depth, Fulmer could be excused for putting in his name as an option to start again. Instead, he is committed to the bullpen.

“We talked about it at the end of last year,” Fulmer said. “I just think the way everything went last year, I kind of got more and more comfortable out of the bullpen to the point where I enjoyed it a lot.

“I love competing. I love showing up to the field every day knowing that I have a chance to pitch that day, instead of once every five days. And I think it helps the team. Obviously, we were in a better spot last year than years previous, and I’m just happy to be a part of it.”

Hinch, in turn, likes having Fulmer in the bullpen as a versatile, veteran arm. Fulmer, after a few fill-in starts in April, was an effective closer for most of May after converting, then reprised the closer role in September after Gregory Soto went on the injured list.

Fulmer saved 14 games and finished seven others. He also had seven relief appearances of two innings or more. Five of his 14 saves lasted four-plus outs.

He’s sitting in the same locker he had last year, but everything else has changed. The generation of pitchers he came up with -- Matthew Boyd, Daniel Norris, even Buck Farmer -- aren’t here, though Boyd and Norris are still free agents. The next generation of starters who were competing against him last spring -- Mize, Skubal and Matt Manning -- currently comprise three-fifths of the projected rotation, as well as the lockers beside him that Boyd, Norris, Farmer and Jordan Zimmermann used to occupy. And Fulmer is now a veteran mentor.

“When I came up, we had [Justin] Verlander, Zimm, Anibal [Sánchez], Mike Pelfrey, Mark Lowe, K-Rod [Francisco Rodríguez] -- I mean, all these guys that obviously had been around forever,” Fulmer said. “So I didn’t really fit in as well in the beginning. And we got there; they were all awesome to me and helped me a lot.

“But I feel like now, with everybody coming up around the same time, I think the chemistry, being around guys, there’s a lot more talking here and on the field. I like where we’re at.”

He has also come full circle. He came to a contending team in 2016 then endured the rebuild. Now, his final season before free agency, the Tigers are on their way out of the rebuild and vying for contention.

“I’m ready to get back to that,” he said.

He’s not quite ready for it to end. If Fulmer can follow up last season with a similar campaign, he could be a valued free agent on the market. He’s just trying not to think about that yet.