TAMPA — Luis Severino could be even better than he was before following Tommy John surgery, according to longtime Yankees bullpen coach Mike Harkey.

“I think when he does come back, he’s gonna be much stronger,’’ Harkey said Saturday of Severino, who is expected to return to the Yankees rotation around midseason after undergoing elbow surgery a little over a year ago.

Harkey’s reasoning lies in the fact that being sidelined gave Severino an opportunity to work on his body in ways he couldn’t when he was preparing for starts every five days.

“If you dig into it, you can do things to your body you weren’t able to when you’re healthy because you have the time,’’ Harkey said.

Harkey was among the Yankees pleased with what Severino did in his first bullpen session since the procedure, a 20-pitch session that featured all fastballs on Tuesday, in which he looked sharp.

“I’ve seen a lot of first-time bullpens after Tommy John, and watching [Severino’s], it was probably the most comfortable I’ve ever seen a player throwing his bullpen and probably the most aggressive I’ve seen from a player,’’ Harkey said.

Severino threw another bullpen session — this one 25 pitches — on Friday and Aaron Boone said there were no issues.

“He’s feeling confident getting on the mound,’’ the manager said. “There’s no apprehension and it’s coming out well.”

Boone had said Thursday that Severino was throwing so well in the Tuesday session, they considered having him back off a bit.

“It looked like there was zero apprehension or worry about whether his surgically-repaired elbow was sound,’’ Harkey said. “That, for me, was probably the biggest thing. He still has probably 20 or 30 more bullpens and a lot more live [batting practices] and games. He’s still a long ways away, but it was a very encouraging first sign.”

Corey Kluber had no complaints about how he felt in his four-inning, 54-pitch outing Saturday, which is the most important aspect of his spring. But the right-hander, who threw just one inning a year ago due to a strained shoulder, said his location wasn’t where he wanted it to be in the Yankees’ 7-5 win over the Pirates at Steinbrenner Field.

He hit a pair of batters and allowed a homer to Tony Stokes Jr. on a pitch that got too much of the plate.

Overall, though, Kluber said he is pleased with where he is at this point of the spring and believes there’s just some “fine-tuning” to be done with his consistency and pitching lanes.

DJ LeMahieu, at second base behind Kluber, thought the right-hander was in good form.

“He looks like himself,’’ LeMahieu said. “The ball’s moving all over the place with his slider and cutter. He looks like I remember facing him, that’s for sure.”

LeMahieu said he has talked with Boone about filling in at first and third base and expects to get in a game at third next week and at first sometime before the end of spring training. … After starting in right field Friday, Brett Gardner was back in left on Saturday.

Darren O’Day whiffed Tony Wolters with a pitch that hit Wolters in the upper leg. Asked if he’d done something like that before, O’Day said he had, but even he was unsure at first if the strikeout would count.

“I was happy because I got the strikeout, but for a second, I thought they had called a dead ball,’’ O’Day said. “It’s a hard game. It really is. I’m not gonna sit here and gloat about [the play].”

Boone said of the odd play, “When you’re a good pitcher with a unique angle, you get some funny swings.”

Right-hander Luis Medina was assigned to minor league camp Friday, but not before impressing Boone following his emergence pitching in winter ball in Puerto Rico this past offseason.

Boone said he liked the 21-year-old’s maturity.

“He came in here with a lot of confidence and with good reason,’’ Boone said. “He’s growing up and showing all the signs of why we’re excited about him.”

Medina appeared in just one game before being reassigned and walked four in two-thirds of an inning.