MESA, Ariz. -- Two years ago, a can't-miss prospect with shaggy hair came to A's camp. The towering lefty drew fervent whispers. Big crowds flanked his bullpen sessions.
Sean Manaea has since graduated to the big leagues. The "Samo-fro" is gone, and the 26-year-old is now readying to team up with Kendall Graveman at the top of Oakland's rotation. In the meantime, another young southpaw has entered the scene. He, too, stands tall. His locks are also long.
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Manaea hasn't gotten much of a look at A's top pitching prospect A.J. Puk, but that will change soon. The 6-foot-7 Puk, whose long blonde hair tucks neatly behind his ears, figures to get ample exposure in his second big league camp. By season's end, he could be in the rotation with Manaea.
"I would think, yeah. He would have to push the envelope, go down and do really well and push his way here," A's manager Bob Melvin said. "That's kind of the way we look at things, anyway."
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All eyes were on Puk, Oakland's No. 2-ranked prospect per MLB Pipeline, when he arranged himself on the six pack of mounds at Fitch Park for his first bullpen session Thursday. The 22-year-old showcased smooth mechanics that produce an easy delivery and not-so-easy-to-hit stuff.
Puk used his first full professional season to expand his repertoire, becoming a four-pitch threat with help from A's Minor League pitching coordinator Gil Patterson. Puk, who a year ago relied almost exclusively on his fastball and slider, brought back his curveball and added a changeup to the mix.
With a full complement, "this guy is a bona-fide starter now," Melvin said.
Though cautioning against burdening him with unfair expectations, Melvin mentioned Hall of Famer Randy Johnson when asked about a starter that reminds him of Puk, the A's 2016 first-round Draft pick.

"You hate to put that kind of expectation or comp on a guy, but there's some similarities, maybe a little different arm angle, kind of the hair, the height and the whole bit," Melvin said.
Melvin even recruited Johnson to talk to Puk and Manaea last spring. Beyond the chatter about simplifying mechanics, Melvin said Johnson spoke "of how you go about your business. It was more kind of the mindset of how to prepare yourself and what to expect and how to be self-driven," he said.
"Just being consistent day in and day out and having that bulldog mentality," Manaea recalled Thursday. "I feel like I could definitely benefit from that. I feel like sometimes I don't have that edge."
Puk finished the 2017 season with Double-A Midland, capping an impressive year that proved productive in both performance and development. He averaged more than 13 strikeouts per nine innings and yielded just three home runs in a combined 125 innings between Midland and Class A Advanced Stockton.
The command is there. A little polishing, it seems, is all that's left for Puk.
"Just come in every day and get better and keep working on my pitches, my mechanics," he said.