Bullpen trade targets for the Mariners

Let's talk about adding reinforcements to Seattle's bullpen. Among the candidates, an entry likely to surprise all of you.

David Zalubowski / AP Images

Early-season injuries to Andrés Muñoz and Penn Murfee served as a reminder to how fragile the balance of a bullpen can be. This rings true again with Murfee back on the IL and Trevor Gott also sidelined. Could these losses and the risk of others casualties occurring prompt the Mariners to pursue relief help this summer?

Perhaps, so I compiled a list of potential trade targets that isn’t all-inclusive. It’s just a sample of eight established relievers I find interesting, plus a ninth name who would be a less conventional addition.

During the selection process, I relied heavily on Expected Weighted On-Base Average (xwOBA). For me, it’s an ideal metric since it reflects a pitcher’s success at minimizing balls in play, preventing men on base, and avoiding damaging contact.

Having said that, not everyone subscribes to using xwOBA like I do - maybe no one else does. So, I included a bunch of conventional and advanced stats in the following tables for your review.

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John Brebbia, RH - Giants

In 2022, Brebbia pitched in a NL-leading 76 games. The Yankees’ 30th round pick in 2011 is once again a valuable workhorse for the Giants with 29 appearances.

It’s worth noting opponents have a 42.9% hard-hit rate against Brebbia (average is 39.9%). Still, the Elon product has managed to hold hitters to a superb SLG, wOBA, and xwOBA despite the frequency of hard contact allowed.

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Brent Suter, LH - Rockies

The soft-tossing southpaw has been exceptional on the road holding opponents to a .139 AVG and .250 SLG. Suter has also been an effective multi-inning arm, logging at least four outs in 17 of 29 appearances. Furthermore, he’s tossed two innings 10 times.

Suter has a low-ish strikeout rate. However, the Harvard alum masterfully avoids damaging contact. His 22.4% hard-hit and 1.7% barrel rates are lowest among 179 pitchers allowing 100-plus batted balls.

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Joe Kelly, RH - White Sox

The ERA, AVG, OBP, and SLG of Kelly won’t thrill fans. But I do like the former UC Riverside Highlander’s superb xwOBA and strikeout rate. The only Seattle relievers with a better strikeout rate than Kelly are Matt Brash (41.8%), Andrés Muñoz (40.6%) and Paul Sewald (35.7%).

Kelly’s 58.6% ground ball rate is 14th-highest among relievers throwing 20-plus innings. Moreover, opponents are hitting just .174 on grounders against the 12-year veteran.

It’s a small sample. But left-handed hitters have been highly successful against Kelly (.925 OPS) compared to righty bats this season (.530 OPS).

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Jake Bird, RH - Rockies

Bird also boasts excellent road numbers. Away from Coors Field, he’s held opponents to a .228 AVG/.279 OBP/.329 SLG with a 26.6% strikeout rate.

The former UCLA Bruin isn’t far behind Kelly with a 56.2% ground ball, which ranks 21st. More importantly, opponents have a lowly .169 AVG on grounders hit off him (average is .227). Perhaps this explains Bird surrendering just two home runs to 190 batters faced.

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Keynan Middleton, RH - White Sox

Middleton, a one-time Mariner, has the tenth-best whiff rate (38.2%) among relievers inducing at least 150 swings. The Oregon native has been particularly lethal against lefty bats holding them to a .307 OPS compared to .731 when facing right-handed hitters.

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Jason Foley, RH - Tigers

Foley is yet another candidate demonstrating a knack for keeping the ball on the ground. He possesses an tenth-best 60.2% ground ball rate with opponents hitting just .220 on grounders. Moreover, the New Yorker hasn’t allowed a home run to 115 batters faced this season.

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Will Vest, RH - Tigers

Vest was a Rule 5 draft pick of Seattle and made his MLB debut with the club in 2021. He was returned to Detroit later that season, but has improved since.

The Texan has a very high 49.3% hard-hit rate (average is 39.9%). But as with Brebbia, loud contact hasn’t deterred Vest from being a solid bullpen contributor for manager AJ Hinch.

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Taylor Clarke, RH - Royals

Pitching home games at hitter-friendly Kauffman Stadium hasn’t helped Clarke’s cause. Visiting opponents have a .292 AVG/.354 OBP/.500 SLG slash-line against the Virginian compared to .205/.280/.273 away from Kansas City.

Nerd alert: Clarke’s 11.8% pop-up rate over the past two seasons is eighth-highest among 190 relievers allowing 200-plus batted balls. For context, Sewald ranks fourth. Pop-ups are almost as beneficial to pitchers as strikeouts producing a .017 AVG.

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Sean Manaea, LH - Giants

Some of you are probably scratching your heads over Manaea’s inclusion, but hear me out. The Giants recently moved the struggling starter to the bullpen as a bulk arm. The preceding table illustrates the former Indiana State Sycamore’s production as a reliever.

Maybe the Mariners could use a multi-inning arm capable of serving as a spot starter. Especially with potential workload challenges facing youngsters Bryce Miller and Bryan Woo and an unknown return date from the IL for Marco Gonzales.

Note: Manaea has one year remaining on his contract. However, he can opt out of the deal. If he doesn’t do so, he’ll earn $12.5 million in 2024.

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Finally

Perhaps the Mariners feel comfortable with their current pool of relief arms and won’t seek additions from outside the organization. Having said that, remaining idle in the reliever trade market seems like a risky proposition to this nerd.

Losing a high-leverage arm like Muñoz or Sewald without additional quality depth in place could have a devastating effect on Seattle’s chances of mounting a second-half surge in 2023.

My Oh My…