System Rankings: #15 - #11
System Rankings: #10 - #6
System Rankings: #5 - Cloud City
System Rankings: #4 - Cleveland
System Rankings: #3 - Brooklyn
System Rankings: #2 - Pittsburgh
It’s no secret that the Mariners have been mediocre for their entire existence. That’s about to change. The Mariners are absolutely loaded with talent -- mainly of the pitching variety. They’ve built so much redundancy into their system that it’s almost impossible to see how they won’t have one of the best rotations in baseball. Even if you think that Sung is a bust, or that Steijns is a reliever, or that Rodriguez’s control will never come around, Seattle still has enough pitching prospects to form an entire rotation of aces and #2s. Oh, and they’ve got the best reliever prospect in baseball, too. The Mariners will have one of the best rotations in baseball for the next six to eight years, and they won’t have to pay a dime for it. Without further ado, the #1 minor league system in baseball: the Seattle Mariners.
#1 - Seattle Mariners
1st in OSA’s rankings, 9 OSA Top 100 (#4 P Miyamoto, #6 P Mitchell, #15 P Avalos, #17 P Steijns, #22 P Sung, #28 P Rodriguez, #66 P Alarcon, #72 P Huerta, #73 3B Guzman)
SP Yoshiomi Miyamoto, 24, #4 OSA, 67 POT, 75 FV - Miyamoto has done absolutely everything asked of him. After being called up to AAA two years ago as a 22-year-old, Miyamoto proceeded to put up 9 WAR over his 51 starts. He’s cut down on his walks every single year and has never allowed many homers. His first 10 starts in the majors have been underwhelming, but he is still very young for the level, and his FIP is a full point below his ERA. The major concern for Miyamoto is the development of his slider. While it projects to be elite one day, it hasn’t shown much development in over a year. If it comes around, he’ll be an ace, one of the best in the game. If it doesn’t, he’ll still make a decent #3 or better. His control and movement still grade out as above-average, and he’s got two other elite pitches to absorb the slider failing to make it. Add in his complete lack of injury history and stamina to go deep into games, and I’m not worried about Miyamoto in the slightest.
SP Jonathan Mitchell, 20, #6 OSA, 69 POT, 80 FV - Mitchell is the second-best pitching prospect in baseball, behind only Mirxayan. Like Mirxayan, Mitchell is extremely developed for his age -- compare him to Miyamoto, who’s 4 years older, if you don’t believe me. Mitchell already has a very good fastball, and it projects to be one of the best in the game when it’s fully developed. His slider’s already above average, and projects to be elite when it’s all said and done. His third pitch is a changeup, and it’s shown consistent development for the past three years. It could be plus one day. Mitchell dominated R-ball last year as a 19-year-old, even with a sky-high BABIP of .355. His ERA this year in A doesn’t tell the full story, as his FIP is a very good 3.2, and he’s increased his K/9 and decreased his BB/9 while moving up a level. If the 80 FV tier were a mountain, Mitchell would be at the very bottom and Mirxayan at the very top. Still, Mitchell is one of the two best pitching prospects in the game, and more than worthy of an 80 FV.
SP Juan Avalos, 23, #15 OSA, 65 POT, 70 FV - Let’s get the major concern out of the way first: Avalos’s control is currently not good. He’s walking far too many batters in AA, and at 23, it’s possible he could never hit his full potential. Now for the good: his control is showing rapid development, including going up 7 points in the past two months. Besides the control, Avalos is everything you want in an ace. He’s already got four plus pitches, and all four of them project in the plus-plus or better range. His fastball tops out a 97 with plus movement. He’s got stamina to go deep in games, if not finish them. Even with all the walks, he’s been above average every single season in the minors, and this year has posted a 3.28 FIP with 10 K/9 in AA. Avalos needs to cut down on his walks, and likely needs to continue his development in AAA, but all signs point to him becoming an ace.
SP Stacey Steijns, 23, #17 OSA, 65 POT, 55 FV - I’m going to be honest, I thought Steijns should’ve been a top 5 pick in the draft. Now, I’m not so sure. His changeup, which has the potential to be among the best in the game, hasn’t developed at all. I know it’s only been three months and he only just turned 23, but it’s definitely a major concern. If the changeup doesn’t develop, he’s a reliever. He doesn’t have two elite pitches to make up for a below-average third one and still start. If the changeup does develop, he’s a legitimate ace. Plus movement, plus-plus control, good velocity and stamina, and can defend his position and control the running game, as well. His performances in the minor leagues mean nothing to me. He can get by with his two plus-plus pitches in the minors, but he’ll get destroyed in the majors without a third pitch.
SP Chao-yang Sung, 24, #22 OSA, 62 POT, 65 FV - The slightly-uglier mirror image of Miyamoto. Miyamoto and Sung’s fates have been tied since they were the first two first-round picks in Seattle’s history, the #8 overall picks in 2028 and 2029, respectively. They’re the same age, have been at the same level their entire careers, and have been close to the same ranking on OSA’s board the entire time. Miyamoto has always put up slightly better stats, however, even if Sung does have the higher potential. Sung is already almost 25, so it’s possible that his pitches will never fully develop. If they don’t, I think he’s still good enough to be a #2 on most staffs. If they do, however, he’s got the potential to be an ace even better than Miyamoto.
SP Esteban Rodriguez, 20, #28 OSA, 63 POT, 60 FV - Like Avalos, Rodriguez’s control is underdeveloped at best. Unlike Avalos, Rodriguez only just turned 20, so he’s got plenty of time to figure it out, and it’s shown a good increase recently. The other big concern is his changeup, which was actually never supposed to develop at all. He came into the league as a two-pitch reliever, and was likely treated as such in his trade with Everett. Now, his changeup is seemingly on its way to being his third plus pitch, with the other two already there. His movement is already plus and his stamina is fantastic, as well. For a 20-year-old, he’s already highly polished, and it’s showing in his performances: this year, he’s putting up a 1.76 ERA across 12 starts in S A. With three or four years before he’ll be ready to pitch in the majors, Rodriguez is a bit of a wild card, but he looks to be well on his way to becoming an ace.
CL Jonathan Alarcon, 21, #66 OSA, 80 POT, 60 FV - Alarcon is hands down the best reliever prospect in baseball. At 21 years of age, he’s already as developed as most of the other relievers on this list. He’s got plus movement, average control with plus-plus potential, and a fastball that touches 99. His fastball is already plus-plus and his sinker is already plus. Both have the potential to be elite. He’s got the stamina to be an everyday closer, but Seattle might want to use him in a fireman type role to maximize his value. His minor league stats are mostly worthless, as he’s been used in a starter role and that’s not his future spot, but he has performed very well there. It’s possible we see Alarcon closing at the major league level this year, which seems insane for someone so young. Reliever prospects are notoriously hard to predict, but Alarcon is by far the closest to being a sure thing.
SP Alvaro Huerta, 23, #72 OSA, 55 POT, 55 FV - Going off of ratings alone, Huerta looks more like a 50 FV to me, but his performance this year in AAA at only 23 has bumped him up a level. He’s decreased his BB/9 by .4 since last year in AA and is currently sitting on a 3.19 FIP. His movement is above-average and his control is on the way to above-average, as well. His velocity is very good, topping out at 98 mph, and he’s got stamina for days. The major concern with him is that he only has two above-average pitches right now, although the fastball is elite and the curveball is plus. He’s got the potential for a third average pitch and a fourth below average one. I think he only needs one of them to develop fully in order to be a #3 starter. If neither of them does, he’s a back-of-the-rotation guy.
3B Raul Guzman, 22, #73 OSA, 60 POT, 55 FV - The first batter on the list, and the only one who projects as better than average. Guzman’s eye is terrible and I’d be surprised if he ever has an OBP of more than about .320. That being said, he’s got raw power that appears to be turning into game power, a good hit tool, and will almost never strike out. He’s got the tools to play an above-average SS, which increases his value for me. Otherwise, he’ll be a very good defensive 3B with a few too many errors to be considered elite. The start to his professional career has been underwhelming, although he’s still on pace to hit 20 HRs in 112 games. If he can turn it around, he’s got the potential to be an everyday starter. If not, he looks like a future super-utility man.
SP Richard Reardon, 21, NR OSA, 53 POT, 50 FV - First of all, the changeup is far away, but it has shown some development this year already. If he hits on all three pitches, he’ll have three elite ones. How likely that is, I’ll leave as an exercise for the reader. Reardon has good velocity, good stamina, good movement, good control, good defending, and is good at controlling the run game. He has the potential to be an ace. I don’t think that’s likely, but it’s certainly there. I think the more realistic outcome is that he becomes a #3 or 4. I’ll need to see him continue his good performance at a level higher than R before I call him anything better than average.
SP Frank Correa, 23, NR OSA, 48 POT, 45 FV - Correa’s control is a bit too far away for me to give him anything higher than 45 FV. His floor is surprisingly low, as well, as he doesn’t have great velocity to make it as a reliever. He’s performed very well so far in AA, and has maintained a consistently good FIP throughout his career. If all of his pitches develop, as does his control, I can see him being a #3, but I think #5 or long-reliever is the more likely outcome.
CF Bob van Keulen, 23, NR OSA, 50 POT, 45 FV - Only the second batter on this list. He’s got the range and arm to play anywhere in the OF at a high level, although his shaky glove will keep him from being elite anywhere. His arm in particular is one of the best in the game. He’s also a fantastic baserunner, although his caught-stealing numbers are alarmingly high for someone so fast. Offensively, he projects to be about average. Might bat .280 and hit 15 to 20 HRs. He’ll never walk much, which limits his value significantly. Regardless, if he keeps developing the way he has, he’ll be a good starter. I think he’ll end up as a decent starter, but a fourth OF is a definite possibility.