Justin Slaten Is More Useful As A Red Sox Trade Chip Than Reliever

[Jordan Leandre]

In every sense of the word, right-handed reliever Justin Slaten has been a major success story as a Rule 5 selection. However, as the Boston Red Sox stare down the barrel of being a deadline seller, shopping him makes the most sense for the organization.

His 6.48 season ERA is incredibly misleading, as he's 15-for-19 in scoreless appearances. In his four outings allowing runs, he's allowed multiple, and twice it's been four. But despite the 6.14 ERA, he's got a 3.90 xERA and 3.31 xFIP across 16.2 innings. His strikeout rate is also at a career-best 26.3 percent, so there's a lot to be encouraged about despite the alarmingly high earned run average.

Having already survived his first season on the big-league roster, Slaten is no longer option-ineligible. Additionally, he's got all three of his options at his disposal to go with three more years of team control beyond 2026. So why does trading him make sense for the Red Sox?

It's hard to gauge how impactful his career has been so far. His rookie season is his only one of more than 35 innings, but the Red Sox missed the postseason entirely. Last year, Slaten had good under-the-hood metrics, but his strikeouts were way down, and injuries limited him to just 36 appearances and 34 innings.

This year, injuries have him at just 16.2 innings. His strikeouts are way up, but the sample size is still so small. Moreover, the Red Sox are closer to the worst record in the sport than postseason contention. So, while he's overall performed well, with a misleading ERA, the team is again hardly reaping the benefits of it.

At the trade deadline, every team is hungry to bolster its bullpen. Even the teams with obvious strengths in the late innings could use another warm body. If for nothing else, to cover against injury. The Red Sox, despite all their faults as a team, have three high-leverage relievers teams have already begun calling about. Four, if you want to count the recent stretch of veteran right-hander Tyron Guerrero. And whether this deadline signifies a full-scale teardown or not, the organization should be entertaining all means of recouping minor league assets, especially on the position-player side.

It feels like a formality that bullpen ace Aroldis Chapman will be traded, but they're listening on everyone and should have a large market on all three. But Slaten, even above Garrett Whitlock, makes sense for the Red Sox to trade.

Justin Slaten's Injuries Are Becoming A Pain Point

Injuries are out of everyone's control in most cases, but some guys find themselves on the shelf more than others. Slaten, even in 2024, spent time on the injured list. Because of this, the Red Sox are almost just as likely to have to work around his unavailability than his production on the field.

His medical records are easily accessible to any acquiring team, but he's still someone with serious arm talent. That said, for the Red Sox, they don't need to stay patient with him in hopes that he's healthy and productive in 2027 or beyond.

It's also important to remember that diddle relievers grow on trees. While a Chapman trade would signal a likely promotion down the stretch for Slaten, one he received at the end of 2024 as well, he's largely used as a hybrid between middle- and high-leverage relief. While incredibly talented, there's not a whole lot about his arsenal that screams eventual breakout, All-Star-caliber reliever.

His sweeper is elite, holding opponents to a .167 average and 50% whiff rate in 2026, but his cutter gets hit hard. His four-seam is underperforming expected data, but serious damage is done against it when it's hit.

Part of why there's a lot of damage done against Slaten when he's off is because hitters have no issues pulling the ball in the air against him. The past two years, he's had Pull-Air rates of 11.6 and 13.7 percent. This year, it's up to 23.8 percent. Sure, it's quite possibly a one-off issue, but it's dramatically hindering his ability to avoid meltdowns when he doesn't have his best stuff. 

Slaten's Remaining Team Control Can Be Exploited By Red Sox

While Chapman -- despite being a rental with a pending option -- is going to fetch the best return for the Red Sox this summer, Slaten having three added years of control makes him an enticing trade chip.

He's not in the echelon of the Mason Millers, the Jhoan Durans, or even the Garrett Whitlocks of the world. What he is, however, is a relatively high-floor arm with high leverage experience. Couple that with team control through the 2029 season, and you have a reliever that'll certainly have intrigue surrounding him this summer.

The silver lining of his bad ERA is the under-the-hood metrics. A 21.1% home runs per fly ball rate is simply unsustainable. As proof of concept, only 19 times has a reliever exceeded that threshold across 40-plus innings since 2002. That's out of 4,119 individual seasons meeting that minimum inning requirement. Likewise, his strikeouts are well above average this season, though he's not a qualified arm yet. He also is 83rd percentile in fastball velocity and extension, meaning he's already got a quality fastball that gets on the hitter a bit quicker than what the radar gun reads.

There's doubt the Red Sox could get a top-100 prospect for Slaten, but they could likely get at least one (and probably two) organizational top-10. Given the volatility of relief pitching, plus the current state of the team, making that kind of trade would be a decent piece of business.

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