Seattle Mariners Continue to Raise Floor, Sign RHP Keynan Middleton

It may have taken some time, but when Jerry Dipoto starts cooking, there’s no stopping him. Coming right off the heels of yesterday’s acquisition of right-handed reliever Rafael Montero, the Mariners today signed yet another righty for their retooled bullpen: Keynan Middleton, formerly of the Angels.

Drafted by Dipoto as a member of the Angels in 2013, Middleton has a potentially electric arm that is still working its way back from Tommy John surgery in 2018. The injury abruptly ended an excellent start to Middleton’s Major League career that saw him earn the closer’s role within his first 36 innings pitched.

Prior to the injury and after, Middleton’s approach remains roughly intact. Often attacking opposing hitters with the fastball, Middleton’s consistently been in the mid-to-high 90s pre- and post-injury. After being a couple ticks off his career average following his return in 2019, Middleton posted a career-high average fastball velo of 97.1 and ranked in the 93rd percentile in fastball spin rate this year. To be fair, though, this is based off of just 12 innings; in total, Middleton’s thrown just 19.2 innings since his injury.

About a quarter of the time, Middleton will dish out a slider that induced a 45.1% whiff rate in his good rookie season in 2017. On the 47 sliders he threw in 2020, 17 of them missed bats. Since his return, Middleton’s leaned on his changeup a bit more than usual, throwing it with decent feel and good spin.

Middleton, who will play the majority of the 2021 season at age 27, just hasn’t been able to locate well since his return. He’s allowed 29 hitters to reach safely, with 13 of those being walks, in just 19.2 innings pitched over the last two years. That may put some people off to this signing, but it’s ultimately an insanely small sample size for a pitcher who’s coming off such a significant injury.

This could be it for the Mariners in addressing the bullpen as they’ve added five arms to the 40-man roster in Montero, Middleton, Kendall Graveman, Domingo Tapia, and Rule 5 selection Will Vest. However, Jeff Passan had them linked to former A’s and Dodgers reliever Blake Treinen prior to the Middleton signing and it’s hard to imagine that one would eliminate the other in this situation.

Buried underneath all this news is the very intriguing decision to DFA outfielder Phillip Ervin. Unless the Mariners are closing in on an extension for Jarred Kelenic, it would appear that there is now a pretty large hole in left field that is currently being filled by – oh no – José Marmolejos.

…Yeah, hopefully they do something about that.


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