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2021 Arizona Diamondbacks Reviews, #34: Humberto Mejía

2021 was a mixed bag for this young man who pitched more in six months than the previous two years combined.

Colorado Rockies v Arizona Diamondbacks Photo by Norm Hall/Getty Images
  • Rating: 3.31
  • Age: 24
  • 2021 Stats: 5 G, 22.1 IP, 7.25 ERA, 5.50 FIP, 1.863 WHIP, 20:9 K/BB, 60 ERA+, -0.4 bWAR
  • 2021 Earnings: League minimum
  • 2022 Status: Pre-arbitration (not arbitration eligible until 2025)


Humberto Mejía’s entry into Major League Baseball was something of a chaotic outlier. Signed as an amateur free agent in 2013, Mejía spent 2015-2019 as a promising but unspectacular member of the Miami farm system. While he regularly performed well, he was still buried behind the likes of pitchers such as Sixto Sanchez, Trevor Rogers, Sandy Alcantara, and even Zac Gallen (for a while). Then Mejía’s fortunes were drastically altered by the perfect storm of events. When COVID struck in 2020, the Miami Marlins were ravaged especially hard. With the season barely announced, Miami found themselves in emergency hiring mode, grabbing warm bodies from the scrap heap just to field a roster. Even these drastic efforts were not enough to provide them with enough pitchers to field a team for a week that had no off-days in it. The result was, they were forced to dig into their farm system to find pitchers. Unfortunately for Miami, they had already done that before hiring cast-offs. That meant they needed to reach even deeper, all the way down to the A+ Jupiter Hammerheads of the Florida State League, where Mejía had pitched a whopping 23.2 innings across five games (four starts) in 2019.

Mejía wound up making three starts for the Marlins that year, before the team finally had some actual MLB pitchers clear COVID protocols. Those starts went about as well as one might expect. At the same time, while Mejía did not have a great deal of success, he hardly embarrassed himself. He struck out more than a batter per inning. He was, however, bitten by the longball and an inability to consistently get strike calls off of his fastball. Three home runs in 10 innings led to a 5.40 ERA against a 6.99 FIP. With Mejía heading back to AA and his service clock already stared, Mike Hazen was able to convince the Marlins to include him in a package with Caleb Smith at the trade deadline.

2021 Review

As expected, Mejía opened the 2021 season in AA Amarillo. He made six starts in Amarillo, getting somewhat mixed results. Mejía’s strikeout and walk totals were quite nice. He posted a K:BB of 37:10 in 32 innings of work. But then, he also allowed 2.0 HR/9. While that part was disturbing, the hyper-inflated offense of the league served to mitigate that as a red flag. Mejía was then given an early-season promotion to AAA-Reno, where he made his first start on 6 June. It was a stinker and a half. He faced 13 batters, walking two and striking out one - in only a single inning of work. His next outing lasted only 23 of an inning in which he faced nine batters, striking out one and walking two more. Then Mejía finally figured out how AAA-Reno works. His next outing was a stellar one. He went six innings, allowing three hits and only one run, which was unearned. He struck out six and didn’t walk any. He took a small step back in his next outing, but was still showing poise and confidence. After that, Mejía rattled off eight consecutive good-to-great outings. This string of successful outings (in Reno no less) resulted in Mejía finally having his name called in late August when injuries, COVID, and ineffectiveness left the Diamondbacks in desperate need of a warm body to start a game.

Mejía made his Diamondbacks debut on 23 August. He allowed only two runs in five innings of work. He struck out seven while walking two and allowing six hits. Given the dumpster fire that was Arizona’s starting pitching at that point in the season, those results were far above and beyond what most hoped for, which was just to find an arm capable of getting out of the third inning without allowing five or more runs. He appeared again when the rotation slot came around the next week and allowed four runs in six innings, after which he was optioned back to Reno. Mejía took the demotion is stride. He made three more starts in Reno, never going less than five innings. His final outing there was a two-run, seven-inning affair. Finally, after more demonstrations of wretched futility by Arizona’s rotation and only two weeks left before the end of the season, Mejía was called back up to the Majors, where he made three more starts. Those starts were not nearly as strong and seemed to be trending in the wrong direction, as he showed signs of late-season fatigue.

2022 Outlook

There is precious little left for Humberto Mejía to prove in the minors. Given that Arizona only has three fully-established starters on the anticipated 26-man roster, Mejía’s name should be ranking near the very top of the list of pitchers given a long look as a regular starter. In 2021, Mejía threw a combined 126 innings. This was 116 more than he threw in 2020 and 35.2 more innings more than he threw in 2019, his previous high mark for workload. It really not at all surprising that Mejía’s final three outings showed signs of fatigue. With a full offseason, Mejía’s strength should be back up and he should have enough life in the arm to be expected to be good for 140-160 innings. There are few pitchers in the Arizona system that can claim such a potential workload. What’s more is, there is no pitcher on Arizona’s system, currently ready to face MLB pitching, who has anywhere near the movement on their fastball as Mejía does. That movement has been both a blessing and a curse for the young right-hander. However, the longer he sticks in the Majors, the more he is going to be able to get calls and the more he is going to learn just what will and will not work with letting that fastball run or dip. Mejía approaches hitters with a fearless mentality, which serves him well. His walks are not a result of trying to paint the corners so much as they come from his fastball simply running out of the zone. This is something that is correctable and something he has shown both an ability and willingness to address.

Short if injury or trade, Mejía should likely be expected to make no less than a dozen starts for the Diamondbacks in 2021. Assuming his performance does not suddenly implode, he could easily make 20-25 starts. Not reaching arbitration until 2025 or free agency until 2028, there is every reason to expect Mejía to be part of the next winning Arizona Diamondbacks team.