OAKLAND -- A.J. Puk got some strange looks in the A’s clubhouse upon his arrival to Summer Camp.

Since joining the A’s as a first-round pick in the 2016 MLB Draft, Puk quickly carved out a distinct look by growing his hair down to his shoulders. But on the first day of camp, Puk showed up to the Coliseum free of his once long flowing blondish hair.

"I had the clippers going on the side of my head and just said to take it all the way off," Puk said. "Some people didn’t recognize me when I first showed up. I told them I was the player [the A’s] got in the [Jorge] Mateo trade [with the Padres].”

The long hair made it easy to compare Puk to Hall of Fame pitcher Randy Johnson, who felt as if he had stepped into a time machine as he watched the 6-foot-7 Puk warming up during a visit to A’s Spring Training in February. Puk may no longer look similar to "The Big Unit” in appearance, but the A’s still expect the big left-hander to bring the heat on the mound, as Johnson once did.

“It’s a personal preference. I’ve been with Randy Johnson over the years, and I kind of liked the similarities, but if he likes it, I’m all for it,” A’s manager Bob Melvin said. “If it makes him comfortable, I’m completely on board with that. But he did have a unique look, and it’s a little different right now. It takes a while to get used to it.”

Puk did more than just chop off his hair during the baseball shutdown, though. Back home in Cedar Rapids, Iowa, he maintained a regular throwing program and worked on his mechanics, looking to get his arm angle higher than it was in the past. He remained in communication with A’s trainers and pitching coach Scott Emerson, even sending over video of his throwing sessions for them to review.

“I was able to clean up some of my mechanics,” Puk said. “I know a lot of Tommy John [surgery] guys come back and go through some shoulder stuff. Hopefully, that’s all in the past.

“Just cleaning up my direction a little bit. My arm angle is a little bit higher right now than what it was. Trying to get more directional instead of pulling off.”

Short hair won’t be the only difference for Puk this year. After a brief stint last September pitching for the A’s out of the bullpen, Puk, Oakland’s No. 3 prospect per MLB Pipeline, enters 2020 expected to move into a starting role.

Had the season started on time, Puk likely would have missed his first few turns through the rotation due to a shoulder strain that led the A’s to briefly shut him down late in Spring Training. Working his way back from Tommy John surgery in 2018, Puk was also expected to be on an innings limit.

Now that the regular season will be 60 games and start July 24, Puk will get a chance to unleash his full potential with a full assortment of pitches and no limitations, a year after he was held back from throwing his curveball and changeup until the final few weeks of the season.

“I probably would have been on an innings restriction,” Puk said. “Now, it’s only 60 games, maybe 12 starts and hopefully some playoff starts. I’m looking forward to starting it.”

Puk's first start will be the first of his Major League career, though it will come in a vastly different atmosphere. While his first two big league appearances in 2019 came in adrenaline-filled games at the Coliseum in front of near-sellout crowds against the Yankees and Giants, Puk’s first start will come in an empty ballpark.

“This year is probably going to be way different,” Puk said. “There’s not going to be any fans hollering at you, so it might be a more relaxed setting. We’ll see how it goes."

The vibe in the stands might be different, though that won’t change Puk’s mindset on the mound.

“I’m not too worried about it,” Puk said. “You still have to go out and execute your pitches.”

Set to slot into a rotation that is also expected to feature Sean Manaea, Frankie Montas, Mike Fiers and fellow top prospect Jesus Luzardo, Puk is excited to see what the A's staff can do fully healthy and together at the same time.

“Every guy in the rotation is talented,” Puk said. “We've got Fiers as the vet. All the guys help each other out and give advice. It’s exciting to think about what can happen.”