The Arizona Fall League is loaded with top prospects, including 15 players from MLB Pipeline's Top 100 Prospects list. However, those aren't the only prospects that will be taking the field on Tuesday when the season begins in Arizona.
The top prospects may be the big draw, but there will also be some hidden gems on the field. With that in mind, here are 30 sleeper prospects -- one from each organization -- to keep an eye on during the Fall League season.
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Blue Jays: Zach Jackson, RHP
Jackson, Toronto's third-round pick from 2016, was highly effective in his first Double-A campaign as he posted a 2.47 ERA while holding hitters to a .142 clip over 43 games. The 23-year-old right-hander's plus curveball is his best weapon, and it helped him to amass 75 strikeouts in 62 innings (10.9 K/9). However, Jackson will need to make major gains with his control after issuing 54 total walks (7.8 BB/9).
Orioles: Jay Flaa, RHP
A sixth-round pick in 2015 out of North Dakota State University, Flaa moved up to Double-A Bowie this year and turned in his best pro season, posting a 2.77 ERA and 0.97 WHIP while holding hitters to a paltry .155 clip over 65 innings (41 games). The 26-year-old right-hander pitches with fringy velocity, operating with an 88-92 mph fastball, but he's effective at mixing in both a curveball and split-changeup and consistently creates good angle to the plate.
Rays: Joe McCarthy, OF (Rays No. 17)
McCarthy's season was truncated by a back injury that cost him nearly three months, but he returned to the field fully healthy in August and helped lead Triple-A Durham to its second straight in the Governors' Cup. The 24-year-old outfielder has long shown an advanced bat and elite on-base skills, and many evaluators expect McCarthy to eventually tap into his above-average raw power from the left side of the plate.
Red Sox: Josh Ockimey, 1B (Red Sox No. 10)
One of three slugging corner-infield prospects Boston sent to the Mesa Solar Sox, Ockimey isn't as famous as Michael Chavis or Bobby Dalbec and can't play third base like they can. The bat speed, strength and loft in his left-handed swing have produced 52 homers in three full Minor League seasons, and he also draws a healthy amount of walks.
Yankees: Matt Wivinis, RHP
Wivinis logged a 5.56 ERA in four seasons of college between Kansas State and Eastern Illinois sandwiched around Tommy John surgery, and he began his career in the independent Frontier League after going undrafted as a senior in 2016. Signed that fall by the Yankees, he had compiled a 1.87 ERA with 123 strikeouts in 86 2/3 innings in two Minor League seasons while reaching Double-A. He works with a pair of high-spin breaking balls he'll throw in any count, and his curveball and slider help his low-90s fastball play up.
Indians: Dalbert Siri, RHP
Signed out of the Dominican Republic in November 2014, Siri tallied a career-high 15 saves while posting a 2.45 ERA and .182 BAA out of the bullpen for Class A Advanced Lynchburg. The 23-year-old righty has power stuff in the form of a mid-90s fastball and sharp slider, and together they helped him rack up 71 strikeouts in 47 2/3 innings.
Royals: Meibrys Viloria, C
After they traded Sal Butera in late August and Salvador Perez sprained his left thumb, the Royals gave Viloria a surprise promotion from high Class A to the big leagues. The 2016 MVP and batting champ (.376) in the Rookie-level Pioneer League, he hasn't posted huge offensive numbers in full-season ball but makes line-drive contact and acquits himself well behind the plate.
Tigers: John Schreiber, RHP
Relievers taken in the 15th round (in 2016) who sign for $6,000 aren't expected to do much in pro ball. But the side-arming right-hander had a 0.54 ERA and .147 BAA in the Midwest League in 2017, then double-jumped to Double-A and posted a 2.48 ERA and .224 BAA with 18 saves in 2018. In his career, he has 153 K's and just 36 walks with a .195 BAA in 137 2/3 IP.
Twins: Griffin Jax, RHP
A product of the Air Force Academy, Jax's performance there in 2016 allowed him to rise to the third round of the Draft. He's had to balance his military responsibilities with his pitching, but is now representing the Air Force in the World Class Athlete Program, meaning he won't be called to active duty. He finished with a 3.70 ERA and 1.52 GO/AO rate in 87 2/3 FSL innings this season.
White Sox: Laz Rivera, SS (White Sox No. 28)
Rivera bounced among three schools during his college career before signing for $1,000 as a 28th-round senior out of NCAA Division II Tampa in 2017. He has batted .309/.365/.471 with 15 homers and 20 steals in 171 pro games, advancing to high Class A while displaying nice feel for the barrel, gap power and average tools as a runner and defender.
A's: Luis Barrera, OF
Barrera was signed by the A's back in 2012 out of the Dominican Republic, but it wasn't until this year that the now 22-year-old outfielder truly put it all together while reaching Double-A for the first time in his career. In 124 games across two levels, Barrera batted .297/.361/.426 with 40 extra-base hits and 23 steals. He's a left-handed hitter who makes a lot of contact and impacts the game on both sides of the ball with his plus speed.
Angels: David MacKinnon, 1B
A two-sport star in college who served as the goalie for Hartford's soccer team, MacKinnon has been an on-base machine in his year-plus of pro ball with a .437 OBP. He started slowly when he got bumped up to the California League this year, but turned it on late by hitting .363/.487/.626 in August which led to a .316/.443/.455 second half.
Astros: Myles Straw, OF
Using an extreme opposite-field approach that yields plenty of singles to right field but little power, Straw won the 2016 Minor League batting title at .358 and has hit .302/.394/.376 in four Minor League seasons. He also offers well above-average speed, a strong arm and plus defense, and was added to the Astros postseason roster after he went 3-for-9 during a September callup.
Mariners: Wyatt Mills, RHP (Mariners No. 9)
Mills, a third-round pick in 2017, scuffled following his August promotion to Double-A but dominated during his time in the hitter-friendly California League, going 6-0 with 11 saves over 35 appearances. He also registered a 1.91 ERA and 0.90 WHIP, and compiled a 49-to-9 strikeout-to-walk ratio in 42 1/3 innings. The 6-foot-3 side-armer's pairing of a low-90s fastball with a tight slider makes him highly effective against same-sided hitters.
Rangers: Demarcus Evans, RHP
Perhaps the most physically imposing player in the AFL, the 6-foot-5, 275-pound Evans had a spectacular year at low Class A Hickory, recording a 1.77 ERA, 103 strikeouts and a .147 opponent average in 56 innings. He has a high spin rate on his 94-96 mph fastball, making it seemingly explode at the plate, and backs it up with a curveball with good depth.
Braves: Ray Patrick-Didder, SS
The Aruban born middle infielder has long tantalized with his plus athleticism and had a breakout season when he hit full season ball for the first time in 2016. He didn't keep that momentum going in 2017 and repeated the Florida State League this past season, but a light seemed to turn on when challenged with a move to Double-A. He's swiped 25 or more bases three years in a row.
Marlins: Tommy Eveld, RHP
Acquired from Arizona for Brad Zeigler at this year's Trade Deadline, Eveld, 24, played football for three years at South Florida before making his college baseball debut as a redshirt sophomore in 2015. He reached Double-A for the first time this year as part of a breakout campaign in which he recorded 16 saves while pitching to a 1.07 ERA with 61 strikeouts in 50 1/3 innings (45 games). A 6-foot-5 righty, Eveld operates at 92-95 mph with a plus slider and above-average control.
Mets: Ali Sanchez, C (NYM No. 25)
There's no question about Sanchez's defensive acumen, with a 47 percent caught stealing rate and raves from catching instructors and pitchers alike. The bat was more of a concern, especially after a .552 OPS in his first taste of full-season ball in 2017. There's still work to be done, but a .681 OPS in 2018 across two levels of A ball is a step in the right direction.
Phillies: Darick Hall, 1B
A 14th-round pick out of Dallas Baptist in the 2016 Draft, Hall opened some eyes by leading the organization in homers (29) and RBIs (101) in his first full season. He repeated the feat in 2018, reaching Double-A in the process. The left-handed power is legit, but he'll need to work on his overall approach (23.9 pct K rate; 5.4 pct BB rate in Double-A) to keep tapping into it consistently.
Nationals: Ben Braymer, LHP
Braymer, 24, was named Washington's co-Minor League pitcher of the year in 2018 after he led Nats farmhands with a 2.28 ERA while going 9-3 with two saves in 28 games (11 starts) between Class A Hagerstown and Class A Advanced Potomac. The left-hander racked up 118 strikeouts -- third-most in the system -- in 114.2 innings pitched, and opposing batters hit just .219 against him. The 6-foot-2 lefty creates good angle to the plate and attacks the zone with a three-pitch mix that's headlined by a solid-average curveball that at times flashes plus.
Brewers: Mario Feliciano, C (Brewers No. 23)
One of the younger players in this year's event, Feliciano, 19, was sidelined for much of the season and will be making up for some of that lost time in the AFL. The No. 75 overall pick in the 2016 Draft struggled to produce when healthy, too, hitting .205 in 42 games with Class A Advanced Carolina, although he did show plenty of offensive potential last year during his full-season debut in the Midwest League.
Cardinals: Lane Thomas, OF
Heading into the 2018 season, Thomas had hit 18 total home runs since the Blue Jays had drafted him in the fifth round of the 2014 Draft. This season, his first full one in the Cardinals organization, the outfielder led the system in home runs with 27 and RBIs with 88, while also stealing 17 bases. After reaching Triple-A, he's knocking on the big league door.
Cubs: Justin Steele, LHP (Cubs No. 8)
Steele was just starting to come into his own when he blew out his elbow in August 2017, but he returned to the mound earlier than expected (11 months later) after Tommy John surgery. He can run his fastball up to 97 mph, also can dodge bats with his curveball and has made encouraging progress with his control and command.
Pirates: Blake Weiman, LHP
A move to the bullpen as a junior at Kansas proved to be a smart one for the left-hander taken by the Pirates in the eighth round of the 2017 Draft. In his first full season, Weiman pitched across three levels, reaching Double-A at the end of the season and finishing with a combined 2.49 ERA and 77/9 K/BB ratio in 67 innings. He reminds some in the organization of former Pirates lefty reliever Tony Watson.
Reds: Ty Boyles, LHP
Boyles hadn't been able to take off as a starter since being taken out of the California high school ranks in the 11th round of the 2013 Draft, but a move to the bullpen this season might be a career-saver. After a 6.85 ERA and .326 batting average against in 10 starts in the FSL, the southpaw posted a 2.75 ERA and .223 BAA as a reliever in the second half.
D-backs: Bo Takahashi, RHP
The Brazilian-born right-hander signed back in December of 2013 and has slowly made his way up the organizational ladder. After a 2017 season that saw him finish with an ERA over 5.00 and not miss many bats, he reached Double-A at age 21 and struck out a combined 9.7 per nine innings while walking only 2.2/9.
Dodgers: Cody Thomas, OF
Thomas originally went to Oklahoma to play quarterback but had more success as an outfielder with the Sooners. He has totaled 39 homers in his two full pro seasons and his raw power ranks among the best in the Dodgers system, though he has to prove he can make consistent contact against quality pitching. He runs well for a 6-foot-4, 211-pounder and has solid arm strength.
Giants: Melvin Adon, RHP (Giants No. 19)
Signed at the relatively ancient age of 21 out of the Dominican Republic in 2015, Adon has progressed slowly yet possesses one of the most electric arms in the Giants system. He sits at 95-98 mph when he starts and has reached as high as 102 mph in shorter stints. Projected as a reliever in the long run, he also has an upper-80s slider that features plenty of power.
Padres: Hudson Potts, 3B (Padres No. 23)
Potts can get overlooked at times simply because he's one of many talented prospects in a loaded Padres system, but the 2016 first-rounder has a big arrow next to his name heading into the AFL after he slashed .260/.335/.455 with 19 homers and 35 doubles while reaching Double-A at age 19. Potts makes a lot of hard contact, with power that already plays to all fields, and he made considerable gains in his approach this year despite accruing more than 140 strikeouts for a second straight season.
Rockies: Justin Lawrence, RHP (Rockies No. 17)
Lawrence barely played as a freshman pitcher/infielder at Jacksonville in 2014, but used his free time to experiment with lowering his arm slot and took off after transferring to Daytona State (Fla.) JC the next spring. He now works in the mid-90s with heavy sink and has posted a 2.42 ERA with 82 strikeouts in 70 2/3 innings between two Class A levels during the last two seasons.
Jonathan Mayo is a reporter for MLBPipeline.com. Follow him on Twitter @JonathanMayo and Facebook, and listen to him on the weekly Pipeline Podcast.
Jim Callis is a reporter for MLB.com. Follow @jimcallisMLB on Twitter. Listen to him on the weekly Pipeline Podcast.
Mike Rosenbaum is a reporter for MLB.com. Follow him on Twitter at @GoldenSombrero.