Wade Miley could be a step up for Seattle, but cost leaves bullpen thin

The Mariners may have upgraded their rotation in acquiring Wade Miley in a trade with the Red Sox, but the cost leaves their bullpen thin.

No general manager has been more active in the young off-season than new Mariners GM Jerry Dipoto, and on Monday he was at it again, making a small upgrade in his starting rotation at a considerable cost in a four-player trade with the Red Sox. That trade sends lefty starter Wade Miley and 25-year-old righty reliever Jonathan Aro to the Mariners in exchange for fellow lefty starter Roenis Elias and would-be Mariners closer Carson Smith.

Dipoto clearly sees Miley as an upgrade on Elias in the Mariners rotation, and he is that, but he’s not such a dramatic upgrade that he was worth five team controlled years of Smith, an extreme groundball-pitcher who emerged as one of the best relievers in baseball as a 25-year-old rookie this past season. Among the 329 pitchers with 50 or more innings pitched in 2015, Smith’s 2.12 fielding independent pitching mark and 1.91 groundball-to-flyball ratio both ranked sixth, his strikeout rate of 32.4% of batters faced ranked 11th, and his opponent’s OPS+ of 54 ranked 17th. He posted all of those rate statistics over 70 appearances and 70 innings and finished in the top 10 in the majors in wins above replacement among pitchers who pitched exclusively in relief this past season. Again, Smith did all of that as a rookie who had thrown just 8 1/3 big league innings prior to the 2015 season.

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In Boston, Smith will join 41-year-old Koji Uehara in setting up newly acquired closer Craig Kimbrel, giving the Red Sox a remarkably dominant Big Three in the bullpen. On a rate basis, Kimbrel actually had the worst 2015 of those three, trailing the pack with a 2.58 ERA, 2.68 FIP, 1.04 WHIP and 3.95 K/BB, while Uehara’s 10.5 K/9 was the lowest of the three. Smith bettered all of those figures and given his extreme groundball rate and the likelihood that he won’t have to make quite as many appearances in the coming season as part of the suddenly formidable Boston bullpen, there is ample reason to expect him to perform similarly despite the move from pitcher-friendly Safeco Field to hitter-friendly Fenway Park.

Elias stands to suffer more from the move to Boston, as he is closer to neutral in terms of his batted ball types. In fact, the Cuban-born Elias has been almost perfectly league average in his tendencies in his first two major league seasons with the exception of a very slightly elevated walk rate. That paints him as a below-average pitcher in a hitting-friendly ballpark, as does his career 93 ERA+ (a figure adjusted for his pitcher-friendly home ballpark). However, Elias is also heading into his age-27 season and coming off a season in which he repeatedly found himself squeezed out of the Mariners’ rotation.

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There’s nothing special about Elias, who will slot in as a back-end starter with the Red Sox at best, but he does have five team controlled years remaining and his left-handedness gives him the safety net of matchup relief work (major league lefties have hit just .218/.304/.332 against him in 259 plate appearances). In Boston, he may prove to be another Felix Doubront, a left-handed starter the Red Sox dumped in advance of his arbitration years, but it’s not absurd to think that he could have proven to be as valuable as Miley had he remained in Seattle.

An All-Star and Rookie of the Year runner-up in 2012, Miley has been little more than a league-average innings eater over the last three seasons for Arizona and Boston. Consider this comparison of Miley’s last three years and Elias’s career numbers: 

Pitcher	ERA	ERA+	FIP	WHIP	K/9	BB/9	K/BB
Wade Miley	4.11	96	3.91	1.36	7.2	3.1	2.33
Roenis Elias	3.97	93	4.23	1.31	7.7	3.5	2.22

Miley has the edge in the key categories of K/BB, FIP, and ERA+. He also has a higher groundball rate (though it has eroded over the last two years) and has established his ability to eat 200 innings a year. Still, Miley’s rates are those of a league-average pitcher at best. He will benefit some from finally escaping his hitter-friendly home ballparks in Phoenix and Boston, but there’s no guarantee that he will be more effective in Seattle for $14.75 million over the next two years (plus a $12 million option for his age-31 season in 2018) than Elias, who is two years younger, could have been at pre-arbitration prices.

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It’s a better bet that Elias will fall short of what Miley could have done in Boston, but the Red Sox have options in their 2016 rotation. The top three of ace David Price, Rick Porcello, who posted a 3.14 ERA with outstanding peripherals in eight starts after missing most of August with a triceps strain, and Clay Buchholz, whose $13 million option was picked up by the team after he missed the second half of the 2015 season with a flexor strain, is established. Behind those three, Boston has sophomore lefties Eduardo Rodriguez and Henry Owens, Elias, fireballer Joe Kelly (7–0 with a 2.35 ERA over his final eight starts of 2015), knuckleballer Steven Wright and rookie Brian Johnson. One-time prospects Rodriguez and Owens will likely have the inside track to the last two rotation spots in camp, that is unless Red Sox president of baseball operations Dave Dombrowski, who said he was likely done making major moves last week, surprises us again.

The ability to acquire five team-controlled years of Carson was worth the reduction in certainty in the rotation for Boston, but it seems unlikely that the price was worth the upgrade to Miley for Seattle. As for Aro, he’s a fairly generic righthanded reliever. He was not a prospect, does not throw especially hard, and is of average size at best. He made his major league debut in 2015 and gave up runs in five of his six major league outings. He put up some good numbers in the minors, but having not signed out of his native Dominican Republic until he was 20, he was older than average for his leagues until this year. He’s hardly any kind of replacement for Smith in the Mariners bullpen, which now appears far more sparse than the Mariners rotation did with Elias.

As things stand, the top three arms in the Mariners’ bullpen are those of 38-year-old trade acquisition Joaquin Benoit, lefty Charlie Furbush, who missed the entire second half of the 2015 season with a rotator cuff tear, and rookie righty Tony Zych, whom the Cubs sold to Seattle in April. Looking at that, it seems safe to assume that Dipoto isn’t done making moves just yet.