Some players are on the verge of stardom, others are entering a crucial phase of their development and still others are getting their first tastes of full-season ball. With the 2018 season approaching, MiLB.com takes a look at the most intriguing prospects from each MLB organization.
Major League ready: A.J. Puk, LHP
Looking at Puk's stat line with Class A Advanced Stockton and Double-A Midland last season, one number jumps out. MLB.com's No. 32 overall prospect racked up 184 strikeouts in 125 innings for a Minor League-leading rate of 13.2 per nine innings. His other numbers weren't too shabby either. He finished 6-10 with a 4.03 ERA, 48 walks and a .227 average against in 27 appearances across both levels.
Puk expanded his repertoire to include a curveball and changeup last season, giving him a starter-quality arsenal that runs four pitches deep when coupled with his plus-plus fastball and plus slider. The 22-year-old was having a solid Cactus League campaign with the big league club this spring, allowing five runs -- four of which came in one start -- on seven hits while fanning seven and walking six over 10 2/3 frames in four appearances before being shut down with left biceps tendinitis. But his status is up in the air after Dr. James Andrews recommended Tommy John surgery Tuesday.
If the sixth overall pick from the 2016 Draft is able to avoid surgery, he will begin the year in Triple-A Nashville, with a trip to the big leagues at some point this season a distinct possibility. Puk's talent is off the charts and his presence would certainly make a difference. But Oakland manager Bob Melvin -- who once compared Puk to Randy Johnson -- said the team will not rush the young southpaw.
"The strides that he's made to get to where he is right now have been very significant," Melvin told MLB.com. "It's just, when you're skipping steps and you haven't had that much time really at the Double-A level, let alone the Triple-A level, you just worry about where you go with him, so we want to make sure he catches all these levels and is that much more prepared once he gets here."
Video: Puk records 13th strikeout of night for Midland
Shining star: Jesus Luzardo, LHP
The first of two prospects acquired by the A's from the Nationals at last year's trade deadline for relievers Ryan Madson and Sean Doolittle, Luzardo will be the most exciting arm in the system once Puk graduates to the Majors. The 20-year-old lefty dominated in limited action last season after missing all of 2016 due to Tommy John surgery, posting a 2-1 record with a 1.66 ERA with 48 strikeouts and five walks over 43 1/3 innings between the complex level and Class A Short Season Vermont.
Lauded for his maturity and polish, Luzardo put together a stellar Cactus League showing, not allowing a run over six innings in three appearances. He opened more eyes by ringing up perennial MVP candidate Mike Trout while holding the Angels scoreless over 2 2/3 frames in his final outing.
"He was really good," Melvin told MLB.com after that start. "This lineup's going to get your attention. I don't care who you are, but at  years old, throwing breaking balls in off counts, up to 97 [mph] that I saw on the radar gun, very poised, it was very impressive to go out and start against this team and look the way he did."
The 2016 third-round pick will break camp with a full-season club -- Class A Beloit -- and should take off with good health and a consistent workload.
Breakout prospect: Sheldon Neuse, 3B
Neuse was the other asset picked up in the Washington deal and quickly showed Oakland that they acquired a solid player. The 23-year-old hit .386 with seven homers in 22 games with Class A Advanced Stockton immediately after the trade, then batted .373 in his final 18 contests after a promotion to Double-A Midland. He didn't stop there either, finishing near the top of the Arizona Fall League in home runs (five), RBIs (23) and extra-base hits (12).
"Neuse was fabulous," A's director of player development Keith Lieppman told MLB.com. "He'll experience different positions and probably be more of a second base/third base-type guy. He's very skillful. He has very good feel for the hand-eye part of the game, real feel for the bat. He's all about baseball. He's awesome at bringing out the best in himself and in others."
Neuse won't maintain that pace over a full season with the A's -- he was hitting .291 with nine homers in 77 games before the trade -- but there is serious cause to believe in his bat. Last year, the 2016 second-round pick struck out some (112 in 117 games) and didn't take a ton of walks (40), but he had 45 extra-base hits last year, drove in 79 runs and stole 14 bases. If he builds on those numbers this season at the upper levels of the Minors, people will have no choice but to take notice.
Video: Neuse blasts three-run dinger for Midland
Loudest tool: Jorge Mateo, SS
Like the two players above him, Mateo joined Oakland at the deadline last season when he was acquired from the Yankees in the package for ace Sonny Gray. It isn't difficult to see why the A's coveted the native of the Dominican Republic. Mateo swiped 52 bases in 129 games last year and has accrued 170 thefts over the past three seasons with a run tool that rates a perfect 80 on MLB Pipeline's 20-80 scouting scale.
The 22-year-old's speed allowed him to leg out a career-high 18 triples and 30 doubles. It translated beyond the basepaths as well, helping him add to his defensive versatility by making 29 appearances in the outfield, though all of those came in the Yankees system. Mateo will likely start the year at Triple-A and his speed should play well in the offensive-friendly Pacific Coast League. It's not out of the question for him to get a look in Oakland later in the year if performs at Nashville.
Full-season debutant: Austin Beck, OF
Taken with the sixth overall pick in last year's Draft, Beck oozes raw potential with the combination of power and speed he brings to the table. Though he put together just a .211.293/.349 slash line in 41 games in the Rookie-level Arizona League in his debut season, the A's brass is enthusiastic over the 19-year-old's ceiling.
"Legitimately looks like a five-tool guy that can do just about everything," Melvin told MLB.com at the Draft. "He throws, he runs, he hits, he hits for power, all the type of things you would hope you would get in a premier first-round pick. He's got all those tools, so we're excited about him."
More to keep an eye on: Oakland's No. 3 prospect Franklin Barreto and No. 5 Dustin Fowler look like good bets to get significant looks in the big leagues at some point this year. Fowler might need a bit more time in the Minors at first, though, since he is coming off a season-ending knee injury. ...Picked up in the same Gray deal as Fowler, righty James Kaprielian also has spent significant time on the shelf. He likely won't start pitching until the middle of 2018 after missing all but three starts the past two seasons with injuries. ...The A's nabbed 18-year-old Cuban outfielder Lazaro Armenteros, the fourth-ranked player on the international market last year. He hit .288 in a solid stateside debut in the Arizona League.
Most home runs in the system: Neuse
Most stolen bases: Mateo
Most strikeouts: Puk
Current prospect to get most Major League playing time: Renato Nunez
Non-Top 100 prospect to end 2018 in the Top 100: Beck