Cole Young needs an obvious change to earn Mariners' trust at second base

The Seattle Mariners are clearly confident in Cole Young. The message coming out during the winter was that the organization was still high on him, and that remains the case even after the trade for Brendan Donovan.

As Daniel Kramer of MLB.com put it, Young would have to "really struggle" during spring training to lose his grip on the starting second base job. But if he does indeed struggle, the M's will have the option of putting Donovan, Leo Rivas or Ryan Bliss at second base, or perhaps even top prospect Colt Emerson if things shake out a certain way.

As much as anything, this could depend on whether Young conquers his nemesis from his rookie season in 2025. Hence the following tip: keep an eye on Young vs. the fastball this spring.

Cole Young has to conquer the fastball to truly earn Mariners' trust

Though Young has the Mariners' confidence, he shouldn't have their trust until he shows he can hit the fastball better than he did in 2025. And in this context, that means "better than not at all."

Against four-seam fastballs, specifically, here's how the 22-year-old fared during his 77-game introduction to the majors last year, vs. the MLB average:

• AVG: .185 vs. .250
• SLG: .250 vs. .434
• Whiff%: 25.0 vs. 21.7

Young's -8 Run Value against four-seamers, meanwhile, was the worst for any Mariners hitter against any pitch.

It's largely because of increasing trouble with the heat that Young lost his handle on his everyday role at the end of 2025. Pitchers began challenging the lefty hitter with fastballs up and on the outer half of the zone, and he just didn't have an answer. He hit .133 and slugged .167 against four-seamers after August.

While Young's whiff rate against the heater wasn't good, it arguably wasn't his biggest problem. His spray chart paints a picture of a hitter who just couldn't get the barrel to the fastball with any authority, instead showing a bunch of ground balls to the right side and lazy fly balls to left field.

Of all the problems a young hitter can have, this might be the scariest.

Bat speed is meant to be an asset that comes with youth, yet Young's was basically average at 71.4 mph last year. A good fastball can not only exploit that, but also render one of his primary strengths relatively moot. He showed strong zone discipline with a 23.5 Chase% last year, but why bother nibbling when you can go right at the guy in the zone with relative safety?

Pitchers figured that out, as Young's four-seamer rate of 42.0 percent was the highest percentage of an individual pitch that any Mariners hitter saw last year. He didn't see any other pitch type more than 12.6 percent of the time.

Given his youth and his obvious talent — dude was a top-100 prospect when the Mariners called him up last year — there's no reason to think Young can't make the improvement he needs to against fastballs. And if he does, we're bound to hear all about how he went about it.

Until that day comes, though, it's a box he has to check. And if it's left unchecked, the confidence the Mariners have in him could be on thin ice.