Seattle Mariners 2021 Top 50 Prospects

Graphic design by John Stewart, @jonance on Twitter

We are just past the two-year mark in the Mariners rebuild (or as Jerry Dipoto calls it, re-tool) which started following the 2018 campaign, and things are trending upwards. The organization has two of the top fifteen prospects in baseball in Jarred Kelenic and Julio Rodriguez (some would argue top ten) and six or seven in the top 100, depending upon who you are asking. For the third straight year, the Mariners have taken a pitcher with their first-round draft pick as they look to solidify their major league rotation for years to come.

Clearly, it is not ideal to have the minor league baseball season cancelled during the first year and a half of a rebuild and we are certain to see the ramifications of this for the Mariners and the rest of baseball in 2021. With only 60 players allowed on each of the taxi squads during the regular season, the rest of baseball’s systems were left to work out on their own. How each system handled that will play a role in the success they have over the next couple of years.


Hopefully, the Mariners will stay on track and end their playoff drought – which currently stands at nineteen years, the longest in all major U.S. professional sports leagues – within the next two or three years. If they can do so, it will be with the help of a number of the prospects on the list you are about to read.

Prospects1500 Tiers:
Tier 1: Players with high expectations of both making the majors and playing at an All-Star level for a number of years
Tier 2: Players with an above average expectation of making the majors and being a solid contributor
Tier 3: Players with an average expectation of making the majors and being a solid contributor
Tier 4: Players who have the potential of making the majors, or have high likelihood of making the majors but providing minimal impact (e.g., middle reliever, low-ceiling UT guys)
Tier 5: Players who are worth keeping an eye on, but likely to never make a team’s 40-man roster

Tier 1:

1. Jarred Kelenic, OF
Age: 21
Highest Level: AA

The organization’s top prospect would have likely made his MLB debut in 2020 had the season not been delayed and shortened. Instead, he routinely put on a show at the alternate training site in Tacoma after arriving with 10-15 pounds of added muscle. He is a five-tool player with plus power and speed to go along with his strong work ethic and drive. There is a strong possibility that he arrives in Seattle during the first half of the year. He figures to play center field to start his career and can also be shifted to either of the corner outfield spots.


2. Julio Rodriguez, OF
Age: 20
Highest Level: High-A

Rodriguez is a physical specimen with huge power potential. After a wrist injury during summer workouts, he had to wait until winter league to get back on the diamond. In Arizona, he displayed his power with a max exit velocity average of 104 MPH. While not a speedster, he has above average base running skills. His MLB debut is at least a season away and when it does come, he will fit nicely in a corner outfield spot alongside Kelenic.


3. Emerson Hancock, RHP
Age: 21
Highest Level: College

Hancock was the Mariners number one pick in the 2020 MLB raft, taken 6th overall out the University of Georgia. He was the third straight college pitcher taken by the organization in the first round. The right hander has plus power with a mid-90s fastball and solid control. He finished his 3-year college career with a 16-7 record along with a 3.47 ERA and a strikeout/walk ratio of 206/55 with 34 of the walks coming in his freshman year.

Tier 2:

4. Logan Gilbert, RHP
Age: 23
Highest Level: AA

Gilbert likely would have joined Kelenic and made his MLB debut in 2020 had there not been a pandemic. He possesses a four-pitch arsenal and has hit 97 MPH with his fastball while displaying a deceptive slider. The right hander looks to be an innings eater and mainstay in the rotation for years to come. Look for him to make his debut in the first few months of the season.

5. Noelvi Marte, SS
Age: 19
Highest Level: Dominican Summer League

After a superb showing in 2019 in the Dominican Summer League, Marte was expected to make his stateside debut with Everett or West Virginia in 2020. Instead, he was sent to the alternate training site and will have to wait to showcase his abilities until this spring. The toolsy shortstop possesses plus power and speed. Look for Marte to move up many prospect rankings during 2021.

6. Taylor Trammell, OF
Age: 23
Highest Level: AA

The speedy outfielder was traded to Seattle in August in the deal that sent Austin Nola to San Diego. The 2018 Futures Game MVP is on his third stop after being originally drafted by Cincinnati. He struggled in AA in 2019 and split time with San Diego and Seattle’s alternate training sites during 2020. His speed is his greatest attribute, stealing 110 bases in 426 games thus far in his minor league career. He is a plus defensively and has deceptive power.

7. George Kirby, RHP
Age: 22
Highest Level: Short Season A

The organization’s top draft pick in 2019 has a solid four pitch arsenal with a fastball that hits the high 90s and a deceptive changeup. He spent 2020 at the alternate training site after being a Northwest League All-Star in 2019. He has plus command striking out 25 batters with zero walks in 2019 with Everett. Look for Kirby to spend most of his time playing AA ball in 2021 and making his MLB debut by the following season.

8. Brandon Williamson, LHP
Age: 22
Highest Level: Short Season A

The organization’s second round pick spent 2019 in Everett with fellow draftee Kirby and subsequently at the alternate training site in 2020. The big lefty stands 6’6” and hits the upper 90s with his fastball and has developed an above average curveball. As with Kirby, I would expect him to spend a good portion on 2021 in AA ball and to make his MLB debut in 2022.

9. Cal Raleigh, C
Age: 24
Highest Level: AA

Raleigh was one of the top hitters in Arizona Instructional League this fall. The 24-year-old was drafted in the third round in 2018 and has developed a nice rapport with the pitching staff. He is a solid defensive catcher whose skills continue to improve and has been impressing the organization with his development at the plate. Look for him to make his MLB debut in 2021.


10. Juan Then, RHP
Age: 20
Highest Level: Low-A

The young right hander was originally signed the organization in 2016 before being traded to the Yankees and subsequently traded back to Seattle. During the instructional league this fall he showed increased velocity hitting the high 90s with his fastball while allowing only one run in 6.1 innings pitched. In addition, he has displayed a nice slider and changeup to complement his fastball. Only 20 years old, there is plenty of room for continued growth as a pitcher.

11. Zach DeLoach, OF
Age: 22
Highest Level: College

DeLoach was the Mariners second round draft pick in 2020 out of Texas A&M and was selected to participate at the alternate training site. He struggled early in his college career before making a swing adjustment and subsequently showed major improvement which led to him winning the Cape Cod batting title in 2019. He is a patient contact hitter with power potential and is above average defensively.

12. Andres Munoz, RHP
Age: 21
Highest Level: MLB

Acquired along with Taylor Trammell in the Austin Nola trade, he had Tommy John surgery last March. Munoz hits 100 MPH plus with his fastball and developed an effective slider. He has had issues with command that still needs to be ironed out. If he can stay healthy, he can be a future closer at the MLB level.

Tier 3:

13. Isaiah Campbell, RHP
Age: 23
Highest Level: College

Campbell was drafted in the Competitive Balance Round in the 2019 Draft and has yet to make his minor league debut. He did get invited to the alternate training site. He displayed a four-pitch arsenal in College and the University of Arkansas with a fastball in the mid-90s. He has shown good control with a terrific strike to walk out ratio.

14. Joey Gerber, RHP
Age: 23
Highest Level: MLB

Gerber made his MLB debut in 2020 going 1-1 with a 4.02 ERA and 1.15 WHIP in 17 relief appearances. His has high velocity in his fastball, a nice deceptive slider and occasionally uses his changeup. He will have a decent shot to remain in the bullpen in 2021 and has future closer potential.

15. Sam Carlson, RHP
Age: 22
Highest Level: Rookie League

Carlson pitched in a game for the first time since 2017 throwing in the Arizona Instructional League this fall when he had Tommy John surgery shortly after being drafted. The organization was excited to be draft him in the second round in 2017 when he was expected to go much earlier. It has been a long road back, but hopefully he will stay healthy and have a strong first full season of minor league ball.

16. Jonatan Clase, OF
Age: 18
Highest Level: Dominican Summer League

Clase was one of the players I was really looking forward to following in 2020 after an impressive performance in the summer league in 2019. He had 31 stolen bases during that campaign and has a 70 plus speed grade. He reportedly has added muscle to his frame and remains one of the more intriguing prospects for the Mariners.

17. Ljay Newsome, RHP
Age: 24
Highest Level: MLB

The right hander got his first taste of MLB action getting a call up in August starting 4 games in 2020. Newsome possesses exceptional command walking just one batter in 15.2 innings this summer. With the Mariners planning on using a six-man rotation in 2021, he will be given a shot to be a starter this year.

18. Austin Shenton, 3B
Age: 22
Highest Level: Low-A

Shenton is a left-handed batter that was drafted in the 5th round in 2019 and spent this summer with the Mariners at the alternate training site. His biggest attribute is his ability to get contact with a smooth swing. He does not have a large power profile or much speed but makes up for it somewhat with his strong work ethic. Despite not being known for his power, he has one of the few players to clear the 29-foot center field wall at Cheney Stadium in Tacoma this summer.


19. Connor Phillips, RHP
Age: 19
Highest Level: College

The Mariners selected Phillips with the 64th overall selection in the 2020 MLB draft. Just 19 years old, he can already hit 98 MPH with his fastball and should continue to grow into his frame. With a high upside, he has the potential to become one of the top prospects in the organization over the next couple of years.

20. Jake Fraley, OF
Age: 25
Highest Level: MLB

After an impressive run through the Minor Leagues, Fraley has struggled in limited action over the past two seasons. In 2020, he appeared in just 7 games in the shortened season. He figures to battle for a roster spot again this spring and should have the opportunity to get more at bats at the MLB level. Jake is still eligible for this list with only 66 at bats in the bigs.

21. Kaden Polcovich, 2B
Age: 21
Highest Level: College

The Mariners selected the second baseman with their third pick in the 2020 Draft. He has an athletic build with above average power and speed. In addition to second base, he can play the outfield and could potentially be a multi-dimensional utility player.

22. Sam Delaplane, RHP
Age: 25
Highest Level: AAA

Delaplane spent the 2020 campaign at the alternate training site and if the season had not been reduced, he likely would have made his MLB debut last year. His fastball can reach the high 90s and throws a hard slider with a curveball grip. He has excellent great command and had 120 K’s in 68.2 innings in 2019.

23. Milkar Perez, 3B
Age: 19
Highest Level: Rookie League

Perez really impressed in the rookie league during the 2019 campaign and looks to have power plus potential. He has an excellent infield arm and looks to be decent defensive third baseman. I am looking forward to seeing his progression during the upcoming season.

24. Damon Casetta-Stubbs, RHP
Age: 21
Highest Level: High-A

The big right hander stands 6’4” and has some power hitting the high 90s with his fastball to go along a couple of breaking balls and a changeup. Add this to his above average command and you may have someone who can start to elevate himself in the prospect rankings further in 2020.

25. Brayan Perez, LHP
Age: 20
Highest Level: Short Season A

Just 20 years old, Perez has above average command with a couple of decent breaking balls to go along with a fastball that sits in the low 90s. He can still fill out his frame and add a little more velocity to his pitches.

26. Adam Macko, RHP
Age: 20
Highest Level: Short Season A

Macko has can hit the mid-90s with his fastball and to go along with a decent changeup and curveball. He was taken in the 7th round in the 2019 draft and is just 20 years old. He has decent command and room for growth in his body frame and velocity.

27. Tyler Keenan, 3B
Age: 21
Highest Level: College

Keenan was drafted in the fourth round of the MLB Draft in 2020 out of the University of Mississippi. The third baseman is 6’4” and 250 pounds, hits with power and is strong defensively. He slashed .403/.488/.791 with 7 HR in 17 games during the shortened college season. Due to his size, there is a decent chance he will end up at first base in the long run.

28. Braden Bishop, OF
Age: 27
Highest Level: MLB

Bishop has been up in the majors for parts of the last two seasons (still only 86 MLB at bats) and has struggled without getting consistent playing time. He is strong defensively and a good baserunner, but the outfield is starting to get crowded with the expected promotion of Kelenic, the pending return of Mitch Haniger and the success of Kyle Lewis there may not be a spot for him in Seattle.

Tier 4:

29. George Feliz, OF
Age: 18
Highest Level: N/A

A five-tool player signed as an international free agent in 2019, Feliz should debut this upcoming season. He has above average power potential and speed, a strong arm with a high ceiling.

30. Kristian Cardozo, RHP
Age: 18
Highest Level: N/A

Signed last year out of Venezuela, the young right hander possesses a three-pitch arsenal with a fastball in the low 90s which will continue to rise with additional size and strength.

31. Aaron Fletcher, LHP
Age: 24
Highest Level: MLB

The left hander struggled in 6 appearances with the Mariners during the short 2020 campaign. He has three good pitches including a mid-90s fastball along with good slider and above average changeup. He will have a good chance to break with the club out of spring training.

32. Matt Brash, RHP
Age: 22
Highest Level: Low-A

The right hander was acquired from the Padres at the trade deadline in the deal that sent Taylor Williams to San Diego. Brash has a three-pitch arsenal with a fastball that hits 96 MPH along with a decent slider and changeup. He looks to likely pitch as a reliever in the majors with an outside shot at becoming a starter.

33. Wyatt Mills, RHP
Age: 25
Highest Level: AA

Mills was disappointed he was not invited to the alternate training site this summer. When he showed up at the instructional league in the fall, he displayed a 97 MPH fastball after previously topping out at 93. In addition to the uptick in velocity, the side armer has high spin rates on both his fastball and slider, in addition to working on adding a changeup. The team protected him from the Rule 5 Draft, allowing him the opportunity to join the club in 2021.

34. Joe Rizzo, 3B
Age: 22
Highest Level: High-A

Coming off a strong year in 2019, there were high expectations coming into 2020. Hopefully, the former second pick in 2016 will be able to pick up where he left off this upcoming year. Rizzo could be used as a utility player in the future.

35. Will Vest, RHP
Age: 25
Highest Level: AAA

The organization claimed Vest in the Rule 5 Draft in December from the Tigers. He can reach the high 90s with his fastball along with a decent slider and changeup. He worked as a closer in the minors and figures to work middle relief in majors.

36. Devin Sweet, RHP
Age: 24
Highest Level: High-A

Sweet has a three-pitch arsenal and above average command. The changeup is his most effective pitch to go along with a mid-90s fastball and a curveball. Swift had an impressive 2019 that he can hopefully build on after a lost 2020.

37. Levi Stoudt, RHP
Age: 23
Highest Level: College

Stoudt was drafted in the third round in 2019 out of Lehigh University. He has above average command with a good changeup, above average curveball, decent slider and a fastball that hits the mid-90s. He was a starter in college and has a chance to remain as such in the majors, though will likely end up in the bullpen.

38. Donovan Walton, 3B
Age: 26
Highest Level: MLB

Walton has had a couple of cups of coffee with the Mariners in 2019 and 2020 playing 12 games over two-year span. A strong defender, he won a Gold Glove with Arkansas in 2019. Along with his solid defense, he is a contact hitter with good baserunning skills. His has an opportunity to carve out a utility player position in the majors.

39. Raymond Kerr, LHP
Age: 26
Highest Level: AAA

Kerr is groundball pitcher with a fastball that hits the high 90s to go along with a slider. Initially a starter, he was converted to relief duties part way through 2019 and looks to be a situational lefty out of the pen.

Tier 5:

40. Dom Thompson-Williams, OF
Age: 25
Highest Level: AA

Thompson-Williams is a good defensive outfielder and above average baserunner who also has some power. He needs to reduce strikeouts and gain consistency.

41. Tim Elliott, RHP
Age: 23
Highest Level: Short Season A

Drafted in the fourth round in 2019, he was Emerson Hancock’s teammate at the University of Georgia. He was invited to the Instructional League this fall striking out 16 in 10.2 innings. He throws four pitches with the changeup being his best. His fastball stays in the low 90s, so an uptick in velocity would improve his long-term chances.

42. Jake Scheiner, 3B
Age: 25
Highest Level: High-A

The third baseman was drafted in 2017 by the Phillies and traded to Seattle in 2019. He has above average power and should play AA ball with Arkansas in 2021.

43. Jack Anderson, RHP
Age: 26
Highest Level: AA

Anderson is a side arm thrower out of the bullpen who had an excellent 2019 as one of the more consistent pitchers in the organization. He figures to start the year in AA with a chance to end up in the Mariners bullpen at some point in 2021.

44. Michael Limoncelli, LHP
Age: 20
Highest Level: High School

Drafted in the sixth round of the 2019 Draft on the same day he had Tommy John surgery, Limoncelli will look to make his minor league debut in 2021. The curveball is his best pitch to go along with a fastball that hits the mid-90s and is adding a changeup to his arsenal.

45. Alberto Rodriguez, OF
Age: 20
Highest Level: Rookie League

Rodriguez was the player to be named later in the deal that sent Taijuan Walker to Toronto last year. He is a contact hitter with some power and is a solid defensive outfielder. He grew up in the Dominican with Noelvi Marte.

46. Adam Hill, RHP
Age: 23
Highest Level: Low-A

Acquired in 2019 in the Omar Narvaez trade, the 6’6” right hander will make his debut in the organization this year. He hits 95 MPH with his fastball to go along with an effective slider and changeup.

47. Carter Bins, C
Age: 22
Highest Level: Short Season A

Bins is an excellent defensive catcher and was invited to the Instructional League this fall. With his skillset behind the plate, he will be given opportunity to develop as a hitter.

48. Jake Haberer, RHP
Age: 25
Highest Level: AAA

Haberer is a hard throwing right hander who struggles with control. If he can resolve the control issues, he will be able to raise in the rankings.

49. Darren McCaughan, RHP
Age: 24
Highest Level: AAA

McCaughan has quality command and has posted good strikeout/walk ratios thus far.

50. Ty Adcock, RHP
Age: 23
Highest Level: College

Adcock was drafted in the eighth round of the 2019 draft out of Elon where he was the team’s closer. He is a hard thrower who hits the high 90s with his fastball and will debut in the Mariners system in 2021.




5 Comments

  1. I’m curious as to how some players can have their ranking and tier change so dramatically in such a short time. For example, Taylor Guilbeau, who was ranked 25 and a tier 3 last year and pitched well in limited playing time with the Mariners, is no longer among top 50 with the Diamondbacks. Where would he be ranked if he was still with the Mariners? Also, why was Matt Festa off your 2020 rankings, when he was ranked number 13 in August 2019? It doesn’t seem to take much for a prospect to lose his high ranking fast.

    Secondly, will the Mariners prospect rankings be updated soon to reflect the international signings?

    • Your question about Guilbeau was answered on the Dbacks column comment. As for recent international signings, short answer is no. Joe may have a follow up article in February or March to address those, but with our publishing 30 different Top 50 columns every day this month, we’re not able to go backwards and update those lists posted before January 15th to add in international signings. If you look at some of them, players whom were expected to sign may have been mentioned in the intro paragraphs, but they could not be ranked as they hadn’t signed yet. Obviously we are including international signings in lists published after the 15th. For those that came out earlier in the month, look for updated midseason Top 50s to include some of these players.

  2. Would’ve liked to see Honeyman on this list and farther up than last time. The yearly improvement the kid has been making is impressive. Gets the bat on the ball a lot, with a nice BA and OBS. Not as much power in the swing as some of these other guys, but he makes good contact nonetheless. I can see the kid at-least getting a shot at the bigs in a few years. Heavily outperforming his 29th round pick.

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