Scouting Report: Merrill Kelly vs. Marlins

Merrill Kelly has been the model of consistency in the Diamondbacks’ starting rotation. The right-hander is 7-3 with a 3.39 ERA in 16 starts this year. He’s struck out 25.0% of hitters while walking just 6.7%.

The most consistent thing about Kelly’s game is his ability to pitch consistently deep in his starts. He’s gone at least five innings in each of his last 14 starts. In that stretch, he’s recorded all nine of his quality starts. That will be crucial as Arizona attempts to establish a tone early in the series against the Marlins.

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Last time out, he held the Rockies to three runs (two earned) over six-plus innings. At the hitter-friendly Coors Field, he held Colorado to six hits, walked three, and struck out seven. He’s punched out at least six hitters in each of his nine starts.

What’s made Kelly successful in 2025 is the ability to command six different pitches, especially the cutter and changeup combination. Opposing hitters are batting .161 against the cutter and .162 against the changeup.

When he has those two pitches working, he’ll put up some impressive strikeout totals. The changeup is his best swing-and-miss pitch, featuring a 36.3% whiff rate. The cutter isn’t a swing-and-miss offering, but it is used to get a lot of called strikes on the backdoor to lefties. Both pitches have a putaway rate, or percentage of two-strike pitches that result in a strikeout, over 25%.

In 2025, Kelly has led with the four-seamer (25%), cutter (24%), and changeup (20%). That’s his bread-and-butter against left-handed hitters. Against righties, he’ll mix in more sinkers and sliders.

Merrill Kelly vs. Marlins

The Marlins rank 23rd with a 92 wRC+ on the season. As a team, that means they are 8% below average.

Despite the poor season numbers, they have some solid hitters that can make Kelly pay for location mistakes. The left-handed hitting Kyle Stowers will be the toughest matchup. He’s slashing .270/.342/.464 with 11 home runs and a 121 wRC+. His home run total is tied with rookie catcher Agustín Ramírez for the team lead.

Kelly has had differing degrees of success against the Marlins over the years. In six career starts, he’s 1-2 with a 5.52 ERA. He has two career quality starts, including one earlier this year.

On April 15, Kelly struck out nine, walked one, and allowed just three hits over six innings in a 10-4 win. It was his first career win against Miami.

Jesús Sánchez is the only current Marlin who faced Kelly prior to this season. He has the strongest stat line, hitting .286 with a home run and a 1.089 OPS in eight career plate appearances. No other hitter has more than three PA against Kelly, with Eric Wagaman and Otto Lopez being the only other hitters with a base hit.