Predicting the additions to the Mariners’ 40-man roster [UPDATED]

Today, Tuesday the 15th at 3 PM PT, is the deadline for the Mariners to add players to their 40-man roster who are eligible for the Rule 5 Draft. For a reminder on how the Rule 5 Draft works, click here, but the tl;dr version is the Rule 5 Draft was instituted to keep organizations from hoarding prospect talent on their minor-league rosters. This is why you’ll see a lot of low-level trades going on during these days as teams try to create space on their 40-man to accommodate the must-adds as well as players they want to protect from the Rule 5 Draft. The Mariners roster is currently at 36.

Update, 12:19 PM: The Mariners have announced they’re adding four players to the 40-man: RHP Prelander Berroa, OF Cade Marlowe, RHP Isaiah Campbell, and OF Jonatan Clase. The surprise here is Clase, who is the only player added who hasn’t played above A ball, but they clearly didn’t want to risk losing the 80-grade speedster with surprising pop and an unmatched work ethic.

Locks:

RHP Prelander Berroa, OF Cade Marlowe

While not officially on the 40-man roster as of this writing, Jerry Dipoto indicated they would be adding Berroa, who was acquired in a minor trade with the Giants for surehanded infielder Donovan Walton. The Northwest League Pitcher of the Year, Berroa has a borderline unacceptable walk rate but maybe the biggest stuff in the organization, with a fastball that kisses triple digits and a hard slider that rack up ugly whiffs. Marlowe was up with the big-league club last year officially as a possible injury replacement, but really as a way to give the youngster an opportunity to experience the environment in the majors, the same tack the Mariners took with Logan Gilbert and Cal Raleigh before their call-up years. Marlowe has hit at every level through the minors, brings above-average speed and defense, and the Mariners love his makeup.

Likely Add:

RHP Isaiah Campbell

The Mariners transitioned the former Arkansas ace into a reliever this year, which likely indicates they’re fast-tracking the 25-year-old to the bigs. Campbell responded to the move to the bullpen in a big way, striking out almost 30% of batters faced in Everett before dominating in 14 games with a late-season promotion to Double-A Arkansas. He’s exactly the kind of reliever who gets snapped up in the Rule 5, so look for him to either be added or traded over these next few days.

On the bubble:

RHP Juan Mercedes, 1B Robert Pérez Jr., RHP Joseph Hernández, OF Jonatan Clase

All three of these players offer upside, but it’s difficult to see other teams adding them for whatever reason. Mercedes is the player with the most experience above Low-A ball, and offers some intrigue to a team who might want to convert the strike-thrower into a reliever, but while he controls the zone well, he doesn’t have the kind of enormous stuff that is usually coveted by teams in the Rule 5. The Mariners held Pérez Jr. down in Modesto to start this season before he forced their hand, literally hitting his way out of Low-A. After the regular season, they sent him to the Arizona Fall League to test his mettle against some tougher competition; he didn’t assuage any concerns about an elevated strikeout rate, striking out over a third of the time, but he also showed his power with a double, a triple, and three homers, as well as putting on a power display in the Home Run Derby, defeating much higher-ranked prospect Heston Kjerstad to win the derby. Hernández, the reigning Cal League Pitcher of the Year, had an excellent year for Modesto, but again lacks that upper-minors experience; he also could use some refinement in the zone, as he posted a double-digit walk rate this year, and his shorter stature (5’11”) might cause some teams to wonder about durability. Clase’s 80-grade speed and burgeoning power would appeal to a team that needs a fourth outfielder, but injuries shortened his year at Modesto and he lacks a track record against higher-level pitching.

Dark horse candidates:

RHP Travis Kuhn, LHP Jorge Benitez

After a strong 2021 where he capped the year with a strong performance in the AFL, Kuhn didn’t take a giant step forward against tougher competition this year at Double-A. If his walk rate was a little lower he’d be definite Rule 5 bait as the slider is an MLB-ready pitch, and the Mariners might still reward him with a roster spot after another solid season. Benitez hasn’t pitched above High-A and also has a double-digit walk rate, but he’s a lefty who strikes a lot of people out and is fresh off a strong performance of his own in the AFL, where he struck out 11 batters in 13 innings.

Eligible, but unlikely to be selected:

RHP Sam Carlson, 3B Milkar Pérez, RHP Devin Sweet, RHP Luis Curvelo

Carlson has battled injuries and didn’t pitch above Low-A Modesto this year. I am far from writing the former second-rounder off, but the likelihood he gets nabbed by another team is low. Pérez had a slow start in Modesto this year as he struggled to acclimate to full-season ball. Sweet was eligible last year and didn’t get selected; he repeated Double-A this year with almost the exact same numbers. Curvelo had an excellent season in Modesto in 2021 that he couldn’t quite repeat at Everett; the stuff remains strong, but he needs more reps against better hitters.