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2020 Arizona Diamondbacks Reviews #30: Keury Mella

Am I the only person who keeps thinking his surname is “Melia”?

Los Angeles Dodgers v Arizona Diamondbacks Photo by Christian Petersen/Getty Images
  • Rating: 3.93
  • Age: 27
  • 2020 Stats: 10.0 IP, 10 H, 3 R, 2 ER, 1 HR, 3 BB, 10 SO, 1.80 ERA, 3,39 FIP, 0.2 bWAR
  • 2020 Salary: league minimum
  • 2021 Status: under team control, less than one year of service time

Firstly, it’s pronounced like this: “CURE-ee MAY-yuh.”

Originally signed by the Giants, Mella had been with the Reds since being traded to them with Adam Duvall, for another future Diamondback, pitcher Mike Leake, at the 2015 trade deadline. He was then the top prospect in the Giants’ system, according to But that probably says more about the weakness of their farm, and Keury didn’t see very much major-league action during his time in Cincinnati. While he appeared for them in each of the last three season, he saw a total of only seventeen innings of work over that trio of campaigns. With an ERA of 7.94, and almost as many walks (12) as strikeouts (13), the lack of playing time made sense.

As did the Reds’ decision to let him go in November last year. He was taken off the 40-man roster, and cleared waivers, but refused the subsequent minor-league assignment, and so became a free-agent. While they apparently had no interest in making a waiver claim, it only took a few days for the Diamondbacks to sign him, and he became a September call-up for the team - not that the term had much meaning this season! The results over the last four weeks were certainly better than you’d have expected, given his major-league track record.

Looking at the Baseball Savant data (and with the usual caveat about small sample sizes), there were some apparently major differences in the pitch arsenal from previous incarnations. Before this year, he relied heavily on his fastball, throwing it 70-80% of the time. But in 2020, he had a relatively even mix between three pitches, adding a slider and a sinker to the mix, with the sinker being his most often-used pitch. But it was the slider, in particular, which seems to have been most effective, being responsible for eight of the ten strikeouts Mella recorded - seven of those being swinging K’s (and the one strikeout looking was an umpire error!).

Below, you’ll find a reel showing a selection of those sliders which Mella threw for swinging strikeouts. It includes what was likely Mella’s most effective outing of the year, on September 7th in San Francisco, when he struck out the side in the bottom of the seventh, on 14 pitches. All three K’s that day came on swings and misses against the slider, as Daniel Robertson, Joey Bart and Mauricio Dubon failed to make contact with the pitch. But it opens with a glorious swing from A.J. Pollock on a pitch nowhere near the zone. As I’ve mentioned before, that shit never gets old...

It’s still a big “if”, but if this does turn out to be Mella finally discovering his mojo, the D-backs could have unearthed a pleasant little gem, It’s clear there was seen as talent being present there in the past, but the key is probably going to be if he can avoid giving up free passes. The slider seems to have been capable of fooling major-league hitters this season, most often by getting them to chase it out of the zone. Should they learn to lay off the pitch, Mella will have to make an adjustment, throwing it nearer the boundary, so that it looks more like a potential strike. Working ahead in the count will help, and he did throw strike one at an above average rate, 65.1%.

The sinker may also prove useful, and it is worth remembering that for almost all his time in the minors, Keury was a starter, with a starter’s repertoire. This was the first year in the major that Mella’s GB/FB rate had been above major-league average, albeit only just at 0.81 compared to 0.78. But that was still a significant improvement over 2017-19, when it had come in at 0.46. We all know how ground-balls can be a reliever’s best friend, especially when it comes to stranding inherited runners (Mella was 3-for-3 there in 2020). A decent sinker would be a valuable weapon on its own terms, as well as helping set hitters up to be put away with the slider.

With several slots open in the D-backs bullpen, after the trades and departures of Archie Bradley, Andrew Chafin, Hector Rondon and Junior Guerra, that’s 27% of Arizona’s relief innings this year which need to be replaced. Under team control through at least the end of 2026, Mella seems like a candidate to take up some of the slack, and could even be a good dark-horse selection potentially to have a breakout 2021 campaign. We can but hope so, anyway!