MESA, Ariz. -- The A’s only began to scratch the surface on their immense depth of pitching with the callups of Jesus Luzardo and A.J. Puk last season. In addition to those southpaws, there are a few young arms in camp this Spring Training who could make an impact in 2020.

Leading the way in that next wave of talent being groomed in the A’s system is Daulton Jefferies, the club’s No. 12 prospect per MLB Pipeline and its top overall right-handed pitching prospect.

After Tommy John surgery in 2017 caused him to miss most of the '18 season, Jefferies put himself back on the prospect radar with a superb '19 campaign that earned him Oakland’s Minor League Pitcher of the Year Award from MLB Pipeline. The 24-year-old righty went 2-2 with a 3.42 ERA, starting the year at Class A Advanced Stockton and finishing up with Double-A Midland. Standing out most to evaluators in the organization was a gaudy strikeout-to-walk ratio in which he racked up 93 strikeouts while walking just nine batters over 79 innings.

That supreme control has continued to open some eyes early in camp during his first two bullpen sessions.

“His walk numbers are off the charts,” A’s manager Bob Melvin said. “He looks good. He’s poised and has a really good delivery. Very rarely does he miss a spot, and at a young age, that’s something that seems to come pretty easy for him.”

No pitcher enjoys walking batters, but Jefferies gets particularly ticked off by the thought of a free pass. That’s why during his rehab from surgery, the right-hander underwent a change in his mentality on the mound. He placed an emphasis on attacking batters, and while he’s not necessarily looking to rack up the strikeouts, he does want to get that first pitch across for a strike as much as possible.

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“I don’t really worry about the strikeout part, I just don’t like walking people. That’s one of my pet peeves,” Jefferies said. “I want to try and get a guy out in three pitches or less. Everything starts with strike one. If you can get strike one, every advantage is key against these guys.”

Next up in his development is to establish more consistency with his slider, a pitch that he began to throw midway through last season, which Jefferies said was more of a “slurve” and led to an uptick in strikeouts. With a fastball that sits around 95 mph and changeup at 89 mph, the slider gives him a much slower pitch that allows him to drop the hammer on unsuspecting hitters at any moment.

“Now we’re just working with the cutter and slider and the different shaping and stuff like that,” Jefferies said. “I got the cutter down, so I think once I start throwing the cutter a lot more, I’ll get a feel for a harder slider. The goal is to do one thing at a time. Fastball, changeup and cutter are all good, now we’re gonna play with the slider a little bit.

“Some days you’ve got the cutter where you can maneuver it to swing-and-misses, and other times you just want to miss barrel. I want the cutter to miss the barrel and the slider to be swing-and-miss.”

The A’s will likely start Jefferies out at Triple-A Las Vegas, where he could join a starting rotation that will also feature promising young pitchers James Kaprielian and Grant Holmes. Now set for a bigger workload after the strict innings limit placed on him last year by the club in an effort to ease him back from injury, Jefferies said that he is excited to "loosen the leash a bit" on his restrictions to really show what he can do over a full season.

Playing in an organization that is not afraid to call up young pitchers in a playoff race, Jefferies could be only a strong first half away from appearing in Oakland, even if it comes in a bullpen role -- like Luzardo and Puk’s in 2019 -- to contribute in a playoff race down the stretch in 2020.

“You can control how much work you put in and some of the results,” Jefferies said. “Everything that has to do with the office upstairs is out of my control. I’m just going to try to push their hand as much as possible.“