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2021 Diamondbacks Reviews: #4 RHP Merrill Kelly

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In a year where the rotation completely fell apart, Merrill Kelly’s consistency stood out.

MLB: Arizona Diamondbacks at San Francisco Giants D. Ross Cameron-USA TODAY Sports

Rating: 6.72

Age: 32 for most of the season

2021 Stats: 27 GS, 7-11, 4.44 ERA, 158 IP, 130 K, 41 BB, 1.291 WHIP, 2.3 bWAR

2021 Earnings: $4.25MM

2022 Status: $5.25MM club option exercised


One of Mike Hazen’s best free agent signings with Arizona belongs to Merrill Kelly. After growing up in Scottsdale and playing his college baseball at nearby Arizona State, Kelly had a weird path to the majors that included a 3-year stop in Korea. After the 2018 season, Kelly signed a 3-year/$9.25MM deal with his hometown team. After a successful rookie year at the Age of 30 that included making 32 starts and putting up a respectable 0.9 WAR season, he had a great start to 2020 that was cut short due to a blood clot in his shoulder that developed as a result of Thoracic Outlet Syndrome. With no record of a pitcher successfully recovering to that injury, there definitely was some concern.

However at the cost of simply $4.25MM, which is pennies for a reliable #4 starter, it was a no-brainer to keep him around. Kelly recovered nicely, suffering no injuries and only missing 5 starts due to contracting COVID in August. In a year where Zac Gallen regressed, Madison Bumgarner continued to look toast, and the other two rotation spots being a carousel, Kelly’s consistency was a huge boost to the team. That type of consistency is something we all appreciated, as Kelly was voted as the best pitcher and Most Valuable Player by Snake Pit readers.

I’m not sure how many more years Kelly has left in terms of being a reliable innings eater, so I see 2022 being his last year with Arizona before hitting free agency. When he’s on, he fills up the strike zone heavily and is able to limit the most damaging type of contact. In 2021, Kelly ranked in the 72nd percentile amongst MLB pitchers in barrel rate, even if he isn’t great at forcing weak contact. He has improved on limiting the type of contact over his time in MLB, seeing his hard hit (95+ MPH exit velocity) rate drop under 40% and a 1% drop in walk rate to 6%. The culmination of improvements in both areas saw his xERA, which is based off his exit velocity data, dropped by nearly a full run from 5.45 to 4.51.

If the team can get another year like 2021 out of Kelly, I consider the whole signing to be a massive success as the team was able to get 3 years of #4 starter production out of him. One thing to be monitoring will be his ability to prevent barrel contact and limiting the walk rate to his 2021 levels to offset the fact he doesn’t miss many bats. He is also a potential trade target for teams looking to pick up a starter at the trade deadline should the Diamondbacks be right around 2022 expectations and on pace for 60-70 wins.