MESA, Ariz. -- Every time that A.J. Puk picked up a baseball over the past two years, doubt crept into his mind.

Overcoming Tommy John surgery in 2018, the left-hander made it back the following year in time to pitch some important innings for the A’s out of the bullpen down the stretch of a run to the postseason in ‘19. But even during that taste of big league success, something just never felt right. It showed the following spring when Puk was shut down from Cactus League action last March due to shoulder discomfort, and again in July when the issue persisted and he landed on the injured list near the end of Summer Camp.

Eventually, Puk underwent season-ending surgery in September that prevented him from appearing in any games for Oakland during 2020.

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After the surgery to clean out his shoulder, Puk, ranked as the A’s No. 1 prospect per MLB Pipeline, is finally feeling like himself again. Living with teammate Jesús Luzardo in South Florida this offseason, the two worked out together at Cressey Sports Performance. Puk specifically focused on implementing a routine developed by trainers at the facility in order to better control his big 6-foot-7 frame, which should allow him to lower the chances of injury and stay on the field.

“I’ve got my body in a good position to come out here and compete,” Puk said. “First and foremost, I just want to prove my health. I want to come out here and be able to play every day. I think I’m in a good position to do that.”

A difference in Puk’s demeanor has been evident in his early bullpen sessions this spring, as his arm action appears much cleaner. Manager Bob Melvin has noticed a more “free and easy” 25-year-old who is no longer concerned about potential setbacks.

“Probably about halfway through my rehab and playing catch progression this offseason, I just completely forgot I had shoulder surgery. Now I just come to the field every day and play catch like nothing ever happened,” Puk said. “That’s what I was looking forward to, because previously for the last year and a half, I was a little hesitant just knowing it would take a while to feel good. Now it’s just ready to go.”

Puk’s journey as a top prospect has not been ideal. Once on the brink of a breakthrough as the expected anchor of the A’s rotation, his career has stagnated over the last year or so. But those who know the type of dominance Puk brings to the mound, like Luzardo -- who developed alongside Puk in the organization throughout the Minor Leagues -- believe that 2021 is the year that Puk makes his full arrival at the big league level.

“I was lucky enough to see him work out and rehab his shoulder this offseason,” Luzardo said. “He’s a grinder. He has that dog in him. I think he’s a breakout candidate this year and is going to open a lot of eyes. I’m excited for him.”

Uncertainty over Puk’s role for this season remains. The A’s plan to build him up as a starter in camp, though with their five starting pitchers from last year’s team still on the roster, the club could opt to utilize the lefty out of the bullpen.

If Puk had it his way, he would choose to start. It is what he has done for most of his amateur and professional career. However, he also understands the position this A’s club is in as it has reached the playoffs in each of the last three seasons and is set to defend its American League West title. Whether it comes in the rotation or out of the bullpen, Puk just wants to come out and contribute with his low-90s slider and fastball that can touch triple digits in any way that he can.

“It’s not how you draw it up in your head,” Puk said. “But if you ask any player, they probably all wish they didn’t get injured. It just comes with the job. You’re going to get injured. It’s all about how you bounce back from it. I just take it on the chin and keep pushing forward and keep rolling.”