Overview
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2025 stats AZ (MLB): 9-6 (12-9) W/L, 22 (32) GS, 128.2 (184) IP, 3.22 (3.52) ERA, 3.58 (3.76) FIP, 3.0 (2.9) bWAR
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Date of birth: 14 October 1988 (age 36 season)
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2025 earnings: $7,000,000
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2026 status: Rejoining the Diamondbacks on a 2-year/$40 million deal with a vesting option for 2028
2025 Review
2025 saw Merrill Kelly enter his seventh season of MLB service, all of which had gone to the Diamondbacks since Mike Hazen poached him from Korea back in 2019. While Arizona’s roster, pitching in particular, endured a terrible rash of IL-bound injuries, Merrill Kelly found a way to continue to post, even if he left a few outings early due to muscle issues. 2025 was the final year which Kelly was under control. This meant that, if Arizona was in the thick of things, he would likely never see another club on his jersey in his career. However, if Arizona stumbled, Kelly and his ability to eat innings in large swaths would be an appealing trade chip.
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Kelly’s Arizona resume is littered with quality outings. In 2025, he produced two games with a game score in excess of 80. His best all-around outing likely came on 18 May against the Colorado Rockies in Phoenix. On a pleasant May evening, Kelly avoided issues with the Chase Field HVAC and tossed seven innings of shutout ball, allowing only one hit and striking out 11 while walking three.
That was one of four games in which Kelly completed seven innings for the Diamondbacks. Of those four games, he allowed a total of only two runs, spread out over two of the appearances. Kelly had an additional two games where he pitched into the seventh inning, giving up a combined four runs. Twelve of Kelly’s 22 starts for Arizona in 2025 were of the quality start variety. In short, until Ryne Nelson finally settled in a bit, Kelly all but carried the entire pitching staff for Arizona in 2025.
Despite Kelly’s best efforts, Arizona had a brutal July and a troubling August. This meant that Kelly was on the trade block, along with Zac Gallen, who was also in the final year of team control. Unlike Gallen, who appears to have let the trade rumour distractions get to him and impact his pitching, Kelly continued to churn out solid outing after solid outing. That is, until the trade deadline passed. Then, Zac Gallen settled in and began to pitch much more like the Zac Gallen that many had come to look up to and Merrill Kelly suddenly hit a brick wall.
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Kelly was moved on deadline day to the Texas Rangers, one of the teams with the least to offer in return. In exchange for 10 starts from Merrill Kelly, the Rangers sent three pitching prospects to Arizona; Mitch Bratt, Kohl Drake, and David Hagaman. TO say that Kelly’s performance for Texas was uninspiring is to be kind. Kelly went from a 134 ERA+ with the Diamondbacks to an abysmal 87 ERA+ with Texas. In 10 starts for Texas, Kelly had three quality starts. He also had three starts where he failed to complete five innings, including an outing where he allowed six runs on nine hits and a walk in only three innings against the Houston Astros. Arizona fans did get to see Kelly one last time as he took the mound for the Rangers when they visited Phoenix. It turned out to be one of Kelly’s better starts for Texas. He pitched seven innings of two-run ball, but took a no-decision in what would eventually be a Texas loss.
2026 and Beyond
From the time Kelly was traded there was rampant speculation that the trade was only a temporary move and that he would eventually return to Arizona. The prognosticators were proven right when Kelly signed a new deal with Arizona on 19 December, a two-year pact with a vesting option for a third season, which would give Kelly his personally-desired 10 years of MLB service time. If he reaches 170 innings pitched in 2027, the 2028 option will vest. That is a mark he has surpassed in four of his six seasons. He came very close in his only other full season, throwing 158 innings in 2021. As of this writing, Arizona will be leaning heavily on Kelly in 2025, as he currently stands to lead the rotation due to the continued rehabilitation of Corbin Burnes. Kelly will be pitching his age 37 season in 2026. He has also put an awful lot of mileage (over 1000 innings) since his return to the States in 2019.
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Kelly will now spend the next two years doing battle with Father Time. Arizona hopes there is still something left in the tank to offset the sizeable contract he penned.