Three Seattle Mariners’ Prospects That Have Disappointed This Year

For the most part, the Seattle Mariners have had a ton of bright spots in their minor league systems. Most of the team’s top prospects have excelled this season, with the likes of Julio Rodriguez, Noelvi Marte, Emerson Hancock, and others flashing the abilities that make them such highly regarded youngsters.

And it’s not just the stars. Players like Cade Marlowe and Carter Bins have broken out in big ways, and have come on to the radar of fans as potential contributors down the line. As a matter of fact, finding three prospects that have been disappointing was challenging. This says a lot about how well the front office has stockpiled depth throughout the system, and how many draft picks and international signings they appeared to have hit on.

But when you have four teams full of prospects, there are going to be guys underperforming. The good news is that most of the guys struggling are borderline guys that didn’t project to have a lot of upside to begin with. And even the guys who may be struggling on the surface, such as Adam Macko (6.23 ERA) have tremendous underlying stats (16.62 K/9, 2.71 FIP). That doesn’t constitute struggling necessarily, more so some bad luck and adapting to the professional levels.

That all being said, there have been some guys the Mariners had hoped for that haven’t performed. Whether it’s because of age, luck, or inexperience these three guys have disappointed to some level over the course of the young season. Here are three Mariner prospects that have disappointed thus far into the 2021 season.

#3: Mariners A-Ball RHP Juan Then – 5 GS, 7.11 K/9, 3.79 BB/9, 4.26 ERA, 4.87 FIP

Then really hasn’t struggled all that much this season, he makes the list largely due to his prospect ranking and the fact that there aren’t a lot of Mariner prospects who have struggled. Fangraphs currently has Then as the No. 11 prospect on their list, and MLB.Com has him as the Mariners No. 8 prospect in the system.

Then’s early struggles aren’t terribly surprising considering he is only 21 and has only thrown 65 innings above Rookie ball. The walks will likely come down with experience, but the low strikeout numbers are a little concerning, especially considering Then sits in the high 90’s with his heater.

What could ultimately be in store for Then, is a move to the bullpen. The heat is there, but he may not have enough of an arsenal to make it as a starter. And it has to be considered that the Mariners have a lot of potential starting pitchers in the system. Logan Gilbert already looks like an MLB pitcher, and both Hancock and George Kirby have been dominant as prospects. It’s not totally out of the question for Then to take the Edwin Diaz route and eventually move to the bullpen.

If Then can continue to develop the fastball and slider combo and add a more consistent change-up, then he should be fine. But as of right now, Then’s 2021 campaign in Everett has been a tad underwhelming.

#1: Mariners Low A-Ball RHP Damon Casetta-Stubbs – 6 GS, 11.52 K/9, 6.12 BB/9, 6.84 ERA, 6.39 FIP

It has been a bit of a nightmare 2021 campaign for the 21-year-old Casetta-Stubbs. The 11th round pick of the Mariners in 2018, the organization was hoping to get an arm with big-time upside and raw talent that could develop down the road.

But that hasn’t happened. Casetta-Stubbs is now in his third year with the organization, and control issues are still lingering in a big way. The BB/9 rate is way too high for a near 22-year-old arm still pitching in Single-A. The strikeout numbers are good and have been good throughout his career, but it’s not enough to counter the walk issues.

The one silver lining for Casetta-Stubbs is that he isn’t getting hit all that much. Opponents are only hitting .219 against him, which does offer hope that if he can limit the walks, he can still be effective. The issue is, there isn’t much to suggest that will be the case. It’s been his biggest problem since making his pro debut, and unless something changes in a big way, it’s hard to see him making it much further in the organization.

Like with Then, it is possible the organization tries to move Casetta-Stubbs to the bullpen but it would like a last-ditch effort to try and find something that works for him.