Mariners Acquire LHP Zach Duke from Twins

Roughly 22 hours away from the non-waiver deadline, the Mariners have made their second trade of the week.

After acquiring right-handed reliever Sam Tuivailala from the Cardinals on Friday, the Mariners have swung a deal for another reliever. This time, a southpaw in Zach Duke.

At 35-years-old, Duke is in his first full season since returning from Tommy John surgery in 2016. The Cardinals took a flyer on Duke last year, not expecting him to be able to return so quickly; however, a fast rehab stint landed him on the Cardinals’ 25-man roster by July.

Duke showed enough to earn himself a one-year, $2.15 million contract with the Twins this offseason. He’s been worth all that and then some.

Duke’s 2.68 FIP is the third-best of his career, slotting him 29th amongst MLB relievers this season. His new left-handed bullpen mate, James Pazos, is just a little bit ahead of him at 25th with a 2.57 FIP.

While his BB/9 of 3.62 is concerning, Duke is also averaging a strikeout per inning (9.40 K/9). Coming from the left side, that’s a real valuable attribute to bring to a bullpen late in the season.

Duke is a traditional LOOGY, though, so there is a handicap in his use. Left-handed hitters are only slashing .237/.274/.288 (.249 wOBA), good enough for 17th best among left-handed relievers this year. But Duke is having a hard time against righties, who are slashing .303/.409/.351 against him.

The Mariners bullpen is pretty deep now, though, so Duke probably won’t get many chances to face right-handed hitters over the next three months.

As you may have noticed on both slash lines, the slugging percentage against Duke is rather low. In fact, perhaps the best note on Duke is that he’s yet to allow a home run all season. Furthermore, Duke has been able to keep the ball on the ground at a 58.8% clip, which is ninth in the MLB.

It appears we have found a trend with the promising GB% of both Duke and Tuivailala. The Mariners are now deviating from their original M.O. of acquiring relievers with high strikeout potential, and instead are going after guys who can rely on their defense and manufacture outs.

As for the compensation, the Mariners aren’t losing a whole lot. Chase De Jong has some potential as a starter but didn’t have an obvious future with the Mariners organization. After floundering in his short amount of time with the M’s last season, De Jong has stayed put in Double-A Arkansas.

In Minnesota, De Jong will be given every opportunity to figure things out. At the very least, he’s earned that. It just wasn’t going to happen in Seattle.

Ryan Costello, on the other hand, was a 31st round selection by the M’s in last year’s draft. In rookie ball, Costello shined with an incredible slash line of .331/.430/.634. He hasn’t been as good in 2018 for Single-A Clinton, but still has the potential to rise quickly through the Twins’ system with his bat.

Considering how up and down the relief market has been lately, that’s the best the Twins could have come away with. If you’re a Twins fan reading this, sorry. It’s not much.

If you’re a Mariners fan (you likely are if you’re reading this), you should be ecstatic, though. Zach Duke is a significant addition to a bullpen that has struggled to find consistency. Duke embodies consistency, and he gives you more flexibility in certain matchups.