It’s my opinion the Seattle Mariner just experienced the most successful player development season in team history. Prospects prospered, the list of “top” prospects doubled, at least, players changed their profiles and projections to the positive, meaningful development took place for literally dozens of minor leaguers.

We saw a handful of graduations — Logan Gilbert, Cal Raleigh, Jarred Kelenic among them — and the club’s current No. 1 prospect has a whirlwind of a season highlighted by massive numbers and answered questions.

A banner year, as one might say.

Every year when you and I have this conversation I am tempted to remind readers this is not about stats. This is not ‘Player of the Year/Pitcher of the Year’ it’s ‘Prospects of the Year,’ which means the criterion is different.

Performance — stats — are helpful, but development and its effect on projected impact are what this is about.

For example, outfielder Cade Marlowe had a great year, batting .272/.365/.563 at two stops this season, including 60 extra-base hits and 23 stolen bases. He was named Mariners Ken Griffey Jr. Minor League Hitter of the Year by the club just this week.

Marlowe experienced his own crucial development this season, but he’s not the hitting prospect of the year because someone else had a more important season, bigger developments, answered more questions about their future.

Make sense?

Here we go.

Hitting Prospect of the Year: Noelvi Marte, SS

Marte, who will not turn 20 until October, was essentially a man-child in Low-A West this season for the Modesto Nuts.

He was consistent, showed plus power, the ability to make adjustments offensively and defensively, and put up numbers worth writing home about, if that’s your thing.

Marte batted .273/.366/.459 with 17 home runs and 24 stolen bases. Moe importantly than those numbers are how he got them.

Marte has plus bat speed that produces easy plus power to his pull side, but his work trying to use the middle of the field more showed power all the way around to the right-center field gap. Opposite-field power that was mostly of the doubles variety right now but very well could turn into legitimate home-run pop as he continues to mature physically and as a hitter.

The right-handed hitting Dominican Republic native was among the elite players at the Low-A level for the first two months of 2021, then had a rough July — .219/.270/.316 with a 27% strikeout rate and just six extra-base hits.

Not only did Marte bounce back in August, he did so in a big way — .287/.412/.553 — and rode it into a short-stint promotion to end the season.

Entering the season the basic questions were whether or not Marte could sustain hit and power production versus pitchers two-plus years his senior, and how much he could improve defensively despite seemingly being on his way to outgrowing shortstop.

He’s listed at 6-foot-1 and 181 pounds, but by multiple accounts is more like 6-2 or 6-3 and around 200 pounds. He’s still athletic and has above-average speed — he entered pro ball with a 70-grade run tool — but has impressively taken a shaky defensive start to 2021 and turned it mostly positive.

Plays he didn’t make early, he made at a high rate the rest of the season. Mistakes he made early, he made at a high rate the rest of the season. Tough plays, routine plays, difficult throws, plays which would be called ‘plus’ plays.

Marte doesn’t have great range, neither laterally nor in terms of coming in on slow ground balls, but he’s cut way down on the routine errors.

Many will look at the 29 error he made at Modesto and think, ‘welp, he can’t field’ and they’d be wrong. He’s not likely to profile well at shortstop, but the plays he’s shown he can make regularly, and the rate at which he’s shown he can make them over an extended stretch, suggest he may end up a solid defender at third base.

Whether Seattle has come to the conclusion he’s not a shortstop remains to be seen. Generally, clubs don’t like moving players off a spot until it’s clear one of two things are true: He can’t play there long term, or his bat suggests, one way or the other, playing elsewhere is necessary (moving Marcus Littlewood from shortstop to catcher rather than third base or the outfield was because the Mariners thought if he could make the transition defensively hit bat might play in the majors. There was a lack of confidence it’d ever play at third or in a corner outfield spot. Moving Marte to third, for example, would be a sign the Mariners believe the bat plays at the hot corner, and there’s tons of evidence it could.)

To some extent, Marte answered every question that could fairly be thrust upon him for the 2021 season, his first full season in pro ball and one that came after an entire year doing nothing but working out at the alternate site in 2020.

He’ll enter 2022 with a chance to mirror the 2021 path of Julio Rodriguez, just like this season his development path mirrored Rodriguez’s 2019 campaign. At this point, Marte’s MLB ETA or probably somewhere between May 2023 and September of that season, but if he keeps answering questions as loudly as he did this season, maybe that’s selling him short.

Runner-Up: Julio Rodriguez, OF

Rodriguez, 20, played half the minor-league schedule and spent time with the Dominican National Team qualifying and then competing in the Olympics. And Rodriguez was good in the Games against far more experienced players.

While stateside, Rodriguez absolutely mashed, finishing at .347/.441/.560 with 13 homers and 21 stolen bases. At Double-A Arkansas, he hit .362/.461/.546 with a strikeout rate of just 18%.

While I don’t project Rodriguez to be an elite hitter in terms of batting average, he’s clearly adept and recognizing when and how to just hit the ball hard and live with the result and when to power up and drive it. Over a full season, by the way, Franchise’s numbers project to 25 home runs, 36 doubles, four triples.

The stolen bases aren’t likely to remain a weapon for him in the big leagues to the extent the totals from this season might suggest, but he’s yet to start losing quickness and speed, despite being all of 6-foot-3 or 6-fooot-4 and 215-225 pounds, maybe more.

Defensively he projects as average from a range perspective, but in a corner could be a high-efficiency glove, and owns a 70-grade arm with increasing accuracy.

He plays the game with tremendous energy and already is a fan favorite, a fact that will only grow with reckless abandon once he reaches The Show.

There are some that still don’t love the entirety of Rodriguez’s swing mechanics, and I see the merits of those concerns, but with plus bat speed and tremendous strength in his hands, wrists and arms, he may not need to make significant fixes, and whether he will have to or not may not be truly learned until he faces big-league pitching regularly. See: Kelenic, Jarred.

Despite 70 raw power, the swing path is clean with limited load. He covers the plate well, and has made an adjustment with his lower half, using his front leg less aggressively without sacrificing timing or power.

It’s just a matter of time before we see it all in the majors.

Over the winter, I’ll document the differences between Rodriguez and Kelenic as hitters and why offensively Rodriguez has always had a slight advantage, and why those exact reasons are why he’s less likely to struggle early.

If Rodriguez had played all year, he’s probably the pick here, and he nearly won out, anyway he was so good, and tackled and conquered so many minors gripes about his game.

Honorable Mentions

Zach DeLoach, OF: .276/.373/.468, 33-2B, 4-3B, 14 HR

DeLoach will have to work on making more contact (24.2% K rate in High-A+Double-A is a tad high for a bat that isn’t likely to hit more than 15-20 homers a year), but he hits line drives, controls the zone, and is above-average defensively in a corner. He doesn’t offer any standout tools, but everything lands in the solid range.

DeLoach is a Top 15ish prospect in an elite farm system because he’s efficient and a high-probability player, even if he lacks the upside of others.

Alberto Rodriguez, OF: .289/.379/.470

Rodriguez, the return from Toronto in exchange for two months of right-hander Taijuan Walker last August, had a really good year and it’s gone largely unnoticed because, well, there are rather large shadows cast by the top five prospects in the organization, including one that shared a clubhouse with Rodriguez all year.

After a bad May, Rodriguez played 100 games the rest of the season — 93 in Modesto, seven for Everett — and batted .317/.403/.511 with 25 doubles, five triples and nine home runs.

During that span, he fanned just 19.7% of the time, walked at an 11% clip, and played an average outfield.

He’s dropped 12-15 pounds, allowing him to compete better allover the field, and there’s probably a little more power to unlock thanks to plus bat speed and a direct swing. But he’s as ‘control-the-zone’ as anyone else in the organization and belongs in the same conversation as DeLoach, Milkar Perez, George Feliz, Gabriel Gonzalez, and has an edge on Corey Rosier, Jonatan Clase, and Starlin Aguilar entering the offseason.

Pitching Prospect of the Year: Matt Brash, RHP

This, despite the presence of the best Mariners pitching prospect since Felix Hernandez in George Kirby, was not even close.

Brash smoothed out his delivery without sacrificing arm speed, displayed a fastball 94-98 mph consistently and deep into starts that included pitch counts into 90s, setting up the best pitch in the system: a power slider with sharp, late, two-plane break.

He hit 100 mph a few times with his four-seamer, there’s run and ride on the pitch, and while his command of it needs to get better, hitters in Double-A just didn’t have a chance.

It’s a 70-grade slider he can vary a bit in shape and velocity. He’ll use the back door with it versus lefties, or go the route of the backfoot tie-up job with the threat of 98 looming.

The data on both pitches are outstanding and project big-league success, including a lot of swing-and-miss.

Brash’s changeup is an underrated pitch to date because he hasn’t thrown it a lot, but there’s fade and sink to it, and he maintains arm speed.

The potential red flags here include 40-grade control — 11.9% walk rate — and some legitimate stink-eye about his arm action. Both suggest a bullpen role is realistic, but he’s athletic, puts in a ton of work and with his raw stuff taking the enormous step forward and in a starting role, perhaps more time can be spent making some small adjustments to combat the issues that were on display in 2021.

But this season was a gigantic win for Brash and the Mariners. He allowed just 63 hits in 97.1 innings split between High-A and Double-A (.180 BAA), and he served up just six long balls.

After posting a 2.55 ERA in 42.1 innings in 10 games for the AquaSox, Brash made 10 starts for Arkansas, and he allowed more than two earned runs just once, and went fewer than five innings just once.

Not one implosion.

Furthermore, over his final seven starts, the Niagara product allowed eight earned runs (1.79 ERA) on 19 hits over 40.1 innings. He walked 17 and struck 59. He did not allow a long ball during that stretch, and opponents batted .137/.231/.165 off him.

Yes, that’s a .137 average and .165 slugging. Four doubles in 156 batters faced was all they could muster.

He struck out over 38% of the batters faced for the year, and had scouts and opposing players talking before every start beginning in June.

Brash is the easy choice for Pitching Prospect of the Year.

Runner-Up: Brandon Williamson, LHP

Williamson had a better year in traditional terms than did Kirby, and isn’t all that far behind in other aspects.

The lefty was the first to be moved up after dominating in Everett (6 GS, 31 IP, 21 H, 10 BB, 59 SO), and essentially doing the same to a better league with much better hitters after the promotion.

Williamson had four games with 10 or more strikeouts, including 25 over a two-game span with the Sox, then posting two more over his final six outings with the Travelers to end the season. But further than that, Williamson struck out fewer than eight batters in just six of 19 starts.

The 2019 second-round pick is a legitimate four-pitch starter, beginning with a fastball up to 96, but mostly 92-94, and occasionally was more 90-93. Most believe, however, Williamson will live 92-95 with a reach-back for 97.

His curveball is his best secondary, but the slider was good in 2021 and helped him dominate lefties (.200 BAA, .336 SLG). His changeup flashed, too, but the curveball was very effective versus right-handed batters, who hit just .239 off him with a .392 SLG.

Williamson is more athletic than some give him credit, and he creates deception with his lower half and front side, helping the fastball play up and hiding the ball from the hitter for a bit longer than is typical. He may not have frontline upside, but I wouldn’t rule it out, and it appears I’m a little more bullish on Williamson than most of the national folks, but those in-tune with the organization seem to see what I’m seeing: a potential No. 2 that has a good chance to see the majors in 2022.

Williamson had a great 2021.

Honorable Mention

George Kirby, RHP

Kirby also split time between Everett and Arkansas, and while the stuff isn’t as gawdy as Brash’s, it’s very good, improved a ton from even June when I saw him at Tri-City, and it comes with plus control and above-average command.

Kirby sat 93-98 mph and as the season wore on, it was more 94-99. He touched 100 or higher on a handful of occasions and topped out at 101.

Despite the spike in velocity, the most important aspects about Kirby’s season and overall profile are why he lands here, and near the top of the prospect rankings, both in the Seattle system, and in Major League Baseball.

Kirby still throws a ton of strikes, and his secondaries all took a meaningful step forward.

The slider is his best offspeed pitch  right now and should miss some bats at the next level, but his curveball isn’t far behind, and his changeup may have more ceiling than either breaking ball.

There’s work to be done in terms of finishing out front on his secondaries, especially with the slider and curveball, and with getting him work. He missed some time as the club went safe with their arms after the year off in 2020, limiting Kirby to 67.2 innings. But he posted an 80-15 K/BB ratio, allowed just one homer all season, and flashed frontline stuff and command.

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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.

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