What to expect from slugging Mariners prospect Montes in bigs

Losers of four straight, the Mariners are in need of some serious firepower to keep from falling too far behind in the AL West and Wild Card races, as they sit five games back in both. They’re about to get some in the form of their No. 5 prospect.

Seattle will call up 21-year-old outfielder Lazaro Montes as part of September roster expansion on Tuesday, MLB.com’s Daniel Kramer reported over the weekend. The Mariners will be in Boston to face the Red Sox at Fenway Park for a three-game series beginning Monday.

Ranked as MLB Pipeline’s No. 56 overall prospect, the left-handed slugger ranks second in the Minor Leagues with 38 home runs over 123 games between Double-A Arkansas and Triple-A Tacoma, and his 63 extra-base hits are tied for fourth-most. His 91 homers lead all Minor Leaguers since the start of the 2024 season; only Dodgers prospect Ryan Ward (who is seven years Montes’ senior) has hit more than 72 in the Minors with 87.

Overall, Montes, who was going to be Rule 5-eligible this offseason, has hit .249/.369/.558 across his two stops, and how he arrives at these numbers highlights how he has a profile with such stark contrasts.

The underlying data proves that the raw power aspect is absolutely real, and it’s the aspect of Montes’ game that the Mariners will bank on showing up loudest in his first appearance in The Show.

In 2026, 360 batters have seen at least 750 pitches in Triple-A. Montes leads that entire group with his 94.9 mph average exit velocity and 57.5 percent hard-hit rate. His 108.8 mph 90th-percentile exit velocity with Tacoma is a touch above Joshua Báez’s 108.5 mark at the Minors’ top level, to use one recently promoted prospect as a point of comparison, and it’s exactly in line with Kyle Schwarber’s 90th-percentile EV in the Majors. With Montes’ 6-foot-5 frame, it is easy to see where that strength comes from, and add in the fact that he does a good job of elevating on contact with more flyballs than grounders, it is easy to see where the homers come from too.

Put plainly: Montes hits rockets … when he does make contact.

It’s the second half of that statement that has been much less consistent through much of the Cuba native’s career, but especially so since he reached the upper levels last year. Montes’ lower half can leak out when he’s trying to get off his monstrous hacks from the left side, making him vulnerable to fastballs up and away, and sometimes he can be so geared up for heat that he becomes defenseless when he begins a swing and a breaking ball dips below his knees, especially one from a lefty.

As such, he’s struck out in 30.6 percent of his plate appearances this season, but that’s only the tip of the iceberg. Among that same aforementioned group of 360 batters who have seen at least 750 pitches in Triple-A this season, Montes has the highest in-zone whiff rate at 34.3 percent; Spencer Jones is his closest competition at 30.9, and only three of the 360 have a mark above 30 percent at all. Montes has an overall whiff rate above 30 percent across all pitch types at Triple-A, regardless of location, and there are some splits issues, too with a .201/.328/.364 line against Double-A and Triple-A lefties (compared to .274/.390/.659 against righties).

That makes it all the more fascinating to see how manager Dan Wilson and his staff will utilize Montes upon his arrival. A below-average runner with plus arm strength, Montes has focused on right field for his entire career in the Minor Leagues. His last appearance at a different position (besides designated hitter) was when he played left on July 15, 2022, in the Dominican Summer League.

Seattle has Julio Rodríguez and Randy Arozarena entrenched in center and left, respectively, and have recently rotated Dominic Canzone, Taylor Ward and Victor Robles in right. Ward has truly struggled with the M’s since being acquired, with a .113/.225/.145 line in 18 games (though he’s been limited at times by left quad tightness). Canzone, who is up to a career-high 20 homers in a breakout year, is widely considered a DH, but it’s unlikely Montes represents a big defensive upgrade over him. The two both hit left-handed anyway. Robles is the best defender of the group but comes with limited offensive upside.

It may be as simple as this. The Mariners need to come out guns a-blazing if they’re going to chase down the Astros in the West or the Guardians in the Wild Card. Montes has a bazooka of a bat. Even if it’s unproven or prone to misfire, that’s artillery you can’t leave in the Pacific Coast League during the stretch run.