Seattle Mariners 2019 Top 30 MLB Prospects Midseason Update

Image credit: Jarred Kelenic (Photo by Tony Farlow)

UPDATE: The Mariners Top 30 now includes all moves made through the July 31 trade deadline. 

The Mariners are in the midst of a rebuilding phase and have infused their farm system with new talent that they hope will make them a more competitive club in the future.

A key area of improvement has been their pitching, as they’ve added righthander Justin Dunn via trade and righthanders George Kirby and Logan Gilbert with their two most recent first-round draft picks. Seattle’s impact position player talent is still very young, headlined by outfielders Jarred Kelenic and Julio Rodriguez. And while improved, the Mariners are still working to get the most out of prized lefthander Justus Sheffield and 2016 first-rounder Kyle Lewis.

The Mariners have a few interesting pieces that could bring back valuable prospects at this year’s trade deadline. They could use Domingo Santana in a trade, as the outfielder is having a good offensive season and has two more years of control before entering free agency following the 2021 season. Another potential trade chip is righthander Roenis Elias, who contenders may view as a useful bullpen piece from the left side. For teams that need catching help, Omar Narvaez has seen a significant spike in power and is getting on base with more consistency.

In return, Seattle must target more pitching depth as they continue rebuilding their farm system.

1. Jarred Kelenic, OF

Kelenic continues to show his plus hit tool and five-tool ability in the minors, receiving an aggressive promotion to the high Class A California League in late May.

2. Julio Rodriguez, OF

Rodriguez’s maturity and advanced bat have allowed him to perform well in his first season stateside, which saw him jump directly to the low Class A South Atlantic League.

3. Justus Sheffield, LHP

Sheffield had to be demoted to Double-A after a very difficult first half. He seems to have responded well to the demotion, although his struggles lend more weight to the concerns he’ll end up as a reliever.

4. Logan Gilbert, RHP

Gilbert’s is rolling against California League competition, as his velocity has ticked back up and he works with two breaking balls that flash plus potential.

5. Evan White, 1B

The defensively-gifted White has made some small tweaks to his swing, which have allowed him to hit well in the offensively-challenging Double-A Arkansas ballpark.

6. Justin Dunn, RHP

Dunn has been consistent at Double-A Arkansas, making the most of a deceptive delivery and the ability to fill up the strike zone.

7. George Kirby, RHP

Kirby has made just one appearance since being taken with the 20th overall pick in this year’s draft, but his four-pitch mix and above-average command make for an exciting potential rotation piece moving forward.

8. Noelvi Marte, SS

The 17-year-old Marte is still far away, but his mature approach at the plate has helped him to a good start in the Dominican Summer League.

9. Cal Raleigh, C

Raleigh is an excellent receiver whose bat showed impact from both sides of the plate at high Class A Modesto. He earned a promotion to Double-A on July 15 after leading the California League in home runs during the season’s first half.

10. Kyle Lewis, OF

Lewis is finally getting consistent at-bats after injuries have hampered him over the past few seasons. His athleticism and ability to make consistent, hard contact at the plate are promising. 

11. Shed Long, 2B

12. Jake Fraley, OF

13. Braden Bishop, OF

14. Sam Carlson, RHP

15. Erik Swanson, RHP

16. Juan Then, RHP

17. Matt Festa, RHP

18. Brandon Williamson, LHP

19. Dom Thompson-Williams, OF

20. Wyatt Mills, RHP

21. Juan Querecuto, SS

22. Taylor Guilbeau, LHP

23. Brayan Perez, LHP

24. Aaron Fletcher, LHP

25. Joe Rizzo, 3B

26. Joey Gerber, RHP

27. Donnie Walton, 2B

28. Anthony Misiewicz, RHP

29. Nolan Hoffman, RHP

30. Jose Caballero, 2B


OF Jarred Kelenic has been as productive as any 2018 first-round pick from the high school ranks, earning a quick promotion to high Class A Modesto.

OF Julio Rodriguez suffered a hairline fracture in his hand but has done a nice job for low Class A West Virginia since returning. Rodriguez has shown the ability to get on-base with consistency and has been a standout prospect in the Mariners’ system this season.

OF Jake Fraley has done nothing but hit in the upper minors, as the center fielder is hitting .314/.383/.550 across both the Double-A and Triple-A levels.

RHP Sam Delaplane is an intriguing name to keep an eye on, having struck out nearly two batters per inning thanks to natural deception and a solid fastball-slider combination.

Although he isn’t ranked in the Mariners’ Top 30, RHP Ljay Newsome has impressed with his deception and ability to avoid barrels despite unimposing stuff. His low-90s fastball and ability to fill up the strike zone have allowed him to keep runs off the board all season.

Taylor Guilbeau, LHP — After posting a 2.52 ERA in high Class A Potomac a year ago, Guilbeau was assigned to Double-A Harrisburg, where he decreased his ERA (2.31), increased his strikeout rate (11.3 per nine) and cut his walk rate (2.6 per nine) while throwing a fastball in the 93-97 mph range. Guilbeau has a power sinker with a solid-average slider and should be an obvious player to protect to avoid losing in the Rule 5 Draft this year, especially now that the Mariners acquired him from the Nationals at the deadline. 

Aaron Fletcher, LHP — Drafted as a college senior out of Houston in 2018, Fletcher has quietly performed during his first two professional seasons and scouts are starting to take notice this year. The 6-foot, 220-pound lefty has a funky delivery that adds deception, but might limit his command and three average pitches in a fastball that touches 94-95 at its best and solid secondaries in a curveball and changeup. There’s not much more than reliever upside with Fletcher, but he racks up strikeouts and generates plenty of weak contact. Like Guilbeau, Fletcher was part of a group of Nationals pitching prospects acquired by the Mariners in exchange for Roenis Elias and Hunter Strickland. 


LHP Justus Sheffield has hit a speed bump in Triple-A, suffering from below-average control while giving up over one hit per inning.

RHP Erik Swanson hasn’t fared well in Triple-A, and his time in the big leagues has been lackluster as well. He throws strikes but hasn’t missed enough bats just yet, raising concerns that he’s an up-and-down starter.


RHP Nolan Hoffman underwent Tommy John surgery recently and is out for the remainder of the season.

RHP Matt Festa dealt with some back spasms in early May but has recovered nicely and is seeing work in the Mariners’ bullpen.

RHP Art Warren has returned to the Double-A Arkansas bullpen after experiencing some shoulder discomfort, which sidelined him for over a month.


1B Dan Vogelbach got called up early this season and hasn’t slowed down with the bat, blasting over 20 home runs so far for the Mariners.

RHP Yusei Kikuchi has been a durable but so far only modestly effective member of the Mariners’ rotation.

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