Initially, I was planning to simply place a group of names here and explain why I think they could rank in the Top 50 next year, or perhaps even push through to the monthly Top 25 updates during the year (when prospects in the majors don’t count or may already have exhausted their eligibility).

Instead, I thought I’d break it up into two sections: One, the most likely minor leaguers to reach the big leagues (whether it be in 2020 or not), and those with the most upside, offering the best chance to take the bigger leap forward in 2020 and beyond.

To avoid listing pretty much every single minor league player in the Seattle Mariners farm system right now, there will be a few interesting players that go unmentioned here. It’s also worth noting I did not automatically list every recent international signing, though it may be warranted in a lot of cases.

Reminder: These names are in >addition to the Top 50, and just because they aren’t noted here OR on the Top 50 doesn’t mean I think they’re bad player and/or cannot make the majors. One has to draw the line somewhere, right?

2020 Prospect Coverage

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Highest Probability Major Leaguers

Luis Liberato, OF
Liberato, 24, is a very good athlete whose tools suggest a chance to play a lot in the majors, but the development to game skills hasn’t taken off just yet.

While it’s unlikely he ends up a regular, the physical gifts keep Liberato in pro ball and could get him to the big leagues in his mid-20s.

Joe Rizzo, 3B
Rizzo is the opposite of Liberato; he’s not a great athlete but the skill portion of his game is solid, and his defense has gotten better the past two years, perhaps making him playable at third base. The issue is the bat.

While he rebounded from a bad 2018 (.241/.303/.321) to hit .295/.354/.423 — amid some swing adjustment, and in a repeat of the Cal League at age 21 — it’s still very difficult to project enough power to profile as an everyday third baseman. Maybe he’s Juan Uribe, but so far that’s all the upside I see.

Darren McCaughan, RHR
Easy low-90s, has touched 95 mph, slightly low three-quarters slot with an average slider that flashes better. It would not be a surprise if McCaughan saw the majors in 2020.

Ian McKinney, LHP
One of the more interesting arms in the system that narrowly missed the Top 50 and could easily have made the Top 40. The 25-year-old McKinney sits 88-91 mph with average command and control, but offers a plus curveball and good deception, inducing strong swinging-strike rates (12.6%) and a 4-1 K/BB rate in Double-A Arkansas in 2019.

He’s undersized at 5-foot-11 and has not displayed a present average changeup, but if he were shortened up in a relief role, there’s probably room for him to sit 90-93 and get through multiple innings with the breaking ball.

Sam Haggerty, UT2
Haggerty is a non-shortstop utility option with no power but has produced good OBPs in the minors. He also offers plus speed and has very good hands and overall defensive instincts that travels well to the outfield.

Haggerty will have to make more consistent contact for the raw OBP skills to play in the majors.

Phillips Valdez, RHR
Valdez sits 92-94 with a four-seam fastball, setting up an average slider and changeup that each offer promise to be more. He’s already 28, so time is of the essence, but he’s started, relieved and has a chance to miss bats. He’s also on the 40-man roster, giving him a leg up on some others in the trek to the majors.

Jack Anderson, RHR
Anderson, 26, was dominant in Arkansas last year with a submarine slot, tremendous sink on the fastball and a slider that plays.

I’d be a bit surprised if he didn’t see the big leagues in 2020.

Anthony Misiewicz, LHR
There’s enough stuff here to suggest a swing man role for Misiewicz and he throws strikes with three pitches. He’s 25, a very good athlete and there’s potential here for more than just a cup of coffee, up-and-down arm.

Misiewicz, an 18th-round pick in 2015, is one of but a handful of players in the system worth discussing that were not acquired by the club with Jerry Dipoto at the helm.

Kyle Wilcox, RHR
Wilcox is another, however.

It’s a power delivery, up to 98 mph and a power curveball, which sounds like a major leaguer until his command and control are brought into the equation. Wilcox issued 49 walks in 61.2 innings last year, but he also whiffed 91 batters.

More strikes and he, too, probably sees the big leagues in 2020.

Nolan Hoffman, RHR
Hoffman’s 2019 was cut short in May when he had to undergo Tommy John surgery and it’s unclear when his 2020 will start — if at all — but a healthy Hoffman is interesting and likely hits the majors as a middle reliever.

He’s sidearm up to 92 mph and the fastball has good sink, generating ground ball outs. His slider is above-average and he has a fringe-average changeup that could help him push his way north without a plus pitch.

Upside Plays

Anthony Tomczak, RHP
The club’s 15th-rounder last June offers present strength and pitchability. He was up to 92 mph prior to the draft and there’s some physical projection left in his 6-2, 195-pound frame.

Blake Townsend, LHP
He’s still raw but flashed last summer in a few chances to throw in the Arizona League. He’s 6-foot-4 and 220 pounds, so while there’s projection, it’s mostly in experience and how he learns to use the physical tools he already possesses.

Throws strikes and has life on the fastball.

Ortwin Pieternella, C/1B
Intriguing offensive skill set for a catcher in that Pieternella can run and offers a dream on the power. Whether or not he sticks at catcher remains to be seen, of course, but the athleticism is there for him to do the job, or move to a corner and be just fine.

Arturo Guerrero, OF
The swing is powerful, producing above-average pop and he generates good leverage, but his overall discipline needs work and the swing gets long quite often.

He’s a good athlete and at 6-foot-3 and 175 pounds, there’s a lot on which to build here. Very interesting long-term project.

Kelvin Nunez, RHP
I think Nunez is a reliever long-term because he’s yet to show a potentially-plus offering, but he has consistent arm speed and 50-grade command of his fastball. He’s still just 20 and command opens a lot of doors.

Axel Sanchez, SS
One of the more interesting of the club’s 2019 international class, Sanchez is a very good athlete with quick feet and enough arm strength to stick at shortstop.

He’s wiry strong and the frame should be able to handle 190 pounds. In the batter’s box the swing might remind some of Alfonso Soriano — but that’s not a player comp, Soriano has insane bat speed with a clean swing.

Robert Perez, 1B
Perez held his own in Triple-A Tacoma for a stretch last year and flashed at least an average hit tool in Everett. He’s a better athlete than his defensive display suggests, but if he’s stuck at first base his path to the majors is going to be tough because there’s not a lot of power upside in the swing and physical profile.

Miguel Perez CF
Perez stands out for his wiry, projectable frame (6-2/170) and while the numbers are ugly (.170/.277/.323) if you look closer the triple-slash told us more good than bad.

He walked 29 times in about 250 PAs as an 18-year-old in the Northwest League where he was nearly three years younger than the average player. He hit five homers and the 150-point differential in his average and slugging percentage tell us there’s some pop to work with here.

He played a lot of right field, but looks like a potential long-stride defender in center. Needs to shorten up some in order to make more contact, but this is a fun developmental opportunity.

Connor Kopach, UT1
Kopach can handle shortstop and has the arm to play some outfield, too. He can really run and has shown legitimate stolen-base ability (41 of 50 as a pro) since being the club’s 25th-round pick in 2018.

Kopach needs to make more contact for the bat to play but he works counts and takes walks. Kopach, for me, is Haggerty after a night’s stay at the Holiday Inn Express.

Max Roberts, LHP
Roberts has always intrigued me and I once called him a potential lefty/poor-man’s Doug Fister. Missed all of 2019 after Tommy John surgery.

Downhill, solid athlete, projectable 6-foot-6 frame…

Adam Macko, RHP
Macko, Tomczak, Tyler Driver and Dutch Landis — all from last year’s draft class — all have a chance to be major leaguers and there’s not a huge difference for me between the group.

Macko offers less physical projection but may have the best present three-pitch mix.

Juan Mercedes, RHP
Mercedes, 20 in April, pounds the strike zone, but the stuff is merely average at present. The breaking ball has a chance to sharpen and be average or better, but he does throw strikes to both sides of the plate.

Osiris Castillo, 2B
Castillo is another candidate for a UT1 role, but has shown some advanced skills at the plate in terms of pitch selection and patience.

Gunn Omosako, RF
Omosako has some tools, including above-average raw power and a plus arm, but he’s coming off shoulder surgery and a missed 2019 season. Like Guerrero, Omosako’s present strength and 6-foot-4 frame offes a good place to start. He’ll be 19 in May.

Nolan Perez, 3B
Perez plays a power position (has the arm and feet to stay there) and takes a big hack, but the swing and game plan aren’t matching up just yet.

He showed barrel ability last summer, but he’s very aggressive and will chase. He’s 21 in May, so time is running out for him to stay on schedule, but the physical tools keep him interesting for another year.

Cesar Izturis Jr., UT1
Another utility type, Izturis lacks strength, but runs well and has terrific hands. I’d like to see him start playing the outfield and even get some time at third base to broaden his defensive horizons, because there’s probably no chance to bat earns him a regular role.

Josias De Los Santos, RHS
De Los Santos will hit the Top 50 next year and he might go further than that. What kept me from ranking him there this year was the straight fastball and below-average control, but there’s profile here I like.

He was up to 94 mph last year in West Virginia and is a far better prospect than Mariners Internet favorite Devin Sweet. JDLS is 20, there’s physical projection at 6-foot-2 and 175 pounds and the breaking ball is average at present. He’s very consistent with his arm speed, but his delivery needs some work.

Jose Aquino, LHP
One of the top two pitching prospects from the 2019 DSL roster, missing bats with a fastball-slider combo and showing a changeup and curveball. Solid athlete with arm speed that could end up sitting 90-94 mph. He’s 6-foot-3 and 180 pounds and will turn 18 in June.

Luis Baez, RHP
After a strong 2018, Baez’s command went backwards in 2019 and he ended up pitching out of the bullpen the final few weeks before being shut down.

It’s a projectable frame (6-3/172) but the step back has to be a concern, whether it’s physical or otherwise. Baez just turned 19, however.

Asdrubal Bueno, SS
Bueno played just 21 games last summer but showed advanced plate discipline and an ability to use most of the field. He’s not real physical yet, but he’s 18 with good bat speed.

Defensively he’s most likely a second baseman or utility option, but has the arm to stick at short.

Jose Caguana, C
Caguana’s power potential led me to him but I’m told there’s a good arm and athleticism to spare. The biggest problem is position. He’s a catcher now, but at 5-foot-10 and 180 pounds, the chances he stays there aren’t good, despite time to add strength — he’ll be 18 in April.

Caguana does a good job generating loft, but he digs in for power a lot, leading to strikeouts, and some overaggressive two-strike swings.

Jose Corniell, RHP
Signed last summer and will likely debut in the DSL in June. He’s 6-foot-3 and 175 pounds, and will be 17 all season. Has shown 85-88 mph fastball.

Deivy Florido, RHS
Florido has a great chance to land in the rankings next year and probably threatens the monthly 25s during the season. He’s mostly 86-89 mph, but the delivery is smooth, the velo is easy and he commands everything well, including a slurvy breaking ball and changeup.

There’s projection left at 6-foot-2 and 165 pounds and he won’t be 20 until the minor league season is complete.

Adbdiel Medina, RHP
Just 5-foot-11, but the arm speed is above-average and he’s already spinning a consistent breaking ball. Turned 18 in January.

Andres Mesa, SS
Mesa is another of the club’s 2019 IFAs and there’s potential for four average tools here.

David Morillo, RHP
He’ll be 18 all season and posted a 41-14 K/BB ratio on the DSL last summer. He’s up to 90 mph with plane and sink, and there’s plenty of projection left.

Joey O’Brien, RHP
O’Brien was a two-way player at the same college that “produced” Bryce Harper, and showed well in six games in 2018 after he was the Mariners’ 6th-round pick. He missed all of 2019 after having Tommy John, but barring setbacks should get back on the mound this summer in the Arizona League.

He’s been up to 93 mph with a cutter, a true slider and a hard changeup, and has toyed with a two-seamer. The biggest downside is he’s 22 with just two games of pro experience.

Milkar Perez, 3B
Milkar doesn’t look like a third baseman but has a chance to produce average power to go with an ability to hit for some average and draw walks. He’ll be 18 all season, and could be a right-handed Kyle Seager in time.

Wilton Perez, RHP
Projectable at 6-foot-3 and 175 pounds and hit upper 80s as a 17-year-old last summer. Good plane, some sink on fastball.

Joseph Rosa, UT2
Rosa is a second baseman for me but has a chance at a big-league reserve type career thanks to 55 speed, contact skills from both sides of the plate, and the ability to work counts and draw some walks. He’s 22 and still needs to add strength, but may see Double-A Arkansas in 2020.

Yeury Tatiz, RHP
Tatiz received the rare mid-season promotion from the DSL and despite a 5.70 ERA battled fairly well in the AZL last summer, striking out 19 in 23.2 innings of work.

The fastball often is straight but when he creates plane from his 6-foot-3 frame and high three-quarters slot, he gets a lot of ground balls. The secondaries all need work, but the changeup, while his rawest pitch, may have the biggest upside. Tatiz won’t be 20 until November.

Luis Veloz, RF
Veloz flashed in two years in the DSL and got a shot in the AZL last summer. He struggled to make contact, but the bat speed and strength are legit and more work with the swing plane could go a long way in his development at the plate.

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Jason A. Churchill

Churchill founded Prospect Insider in 2006 and spent several years covering prep, college and pro sports for various newspapers, including The News Tribune and Seattle PI. Jason spent 4 1/2 years at ESPN and two years at CBS Radio. He now serves as the Executive Copy Editor at Data Skrive, a tech company that manipulates data to provide automated content to clients including the AP, BetMGM, USA Today, and ESPN. Find Jason's baseball podcast, Baseball Things, right here.