Diamondbacks Pitcher Merrill Kelly's Real Test Begins Now

This feels like it could be a turning point for Arizona's righty.

Apr 21, 2026; Phoenix, Arizona, USA; Arizona Diamondbacks pitcher Merrill Kelly against the Chicago White Sox at Chase Field. Mandatory Credit: Mark J. Rebilas-Imagn Images | Mark J. Rebilas-Imagn Images

The Arizona Diamondbacks have been needing better production out of right-handed veteran starter Merrill Kelly for some time. That began in his most recent start, as Kelly delivered a high-quality seven-inning start against the struggling New York Mets offense.

But Kelly's ERA is still a lofty 7.62, and his expected ERA is a worse 9.93. He's been hit quite hard all season, and has somehow still gotten a bit lucky in terms of actual results.

His last start was a step in the right direction. He got deep into a game and seemed to look more like his old self as the outing progressed. That is a good sign, to be sure. But Kelly is about to face the Colorado Rockies, in the high-octane environment of Coors Field. The elevation will not be kind to high exit velocity, and Kelly may struggle as a result.

But he also has historic success against Colorado. If Arizona wants its veteran right-hander to get back into a rhythm, he has to display that improved command in a less-than-ideal environment, and for the second straight start.

Diamondbacks' Merrill Kelly's history vs Rockies

May 3, 2026; Chicago, Illinois, USA; Arizona Diamondbacks pitcher Merrill Kelly (29) pitches against the Chicago Cubs during the first inning at Wrigley Field. Mandatory Credit: Patrick Gorski-Imagn Images | Patrick Gorski-Imagn Images

In 17 career appearances against the Rockies, Kelly has an excellent 3.25 ERA, and holds an impressive 9-3 record. He's struck out 102 Rockies batters in 108 career innings against Colorado.

Surprisingly enough, his numbers are decent at Coors Field, as well. Kelly holds a 4.12 ERA and 4.41 FIP in the mile-high stadium environment. Considering the offensive haven, that is a relatively encouraging track record.

It's worth noting, however, that the Rockies' offense this season has been top 10 at home, and has crept up a bit from the bottom in away games, as well. Colorado's lineup has been producing, and they're already well capable of slugging in their home ballpark.

So Friday night's start will still be a challenge for Kelly, no doubt. A 17-27 Rockies record means nothing at this ballpark.

Diamondbacks need Merrill Kelly turnaround to continue

Apr 21, 2026; Phoenix, Arizona, USA; Arizona Diamondbacks pitcher Merrill Kelly reacts in the first inning against the Chicago White Sox at Chase Field. Mandatory Credit: Mark J. Rebilas-Imagn Images | Mark J. Rebilas-Imagn Images

The fact is, this will be Kelly's sixth start of the season, after beginning the year on the Injured List thanks to a back issue.

While it was certainly understandable to see plenty of rust out of Kelly in his first handful of starts — and there was plenty of it — he's no longer in a ramp-up phase. There should be clear signs of command returning at this point.

It was around Kelly's fifth and sixth starts in 2025 that he truly began to find his rhythm, after an eerily-similar poor start despite being fully healthy.

So while perfection is not necessarily expected out of Kelly, especially at Coors Field, the Diamondbacks simply need the 37-year-old veteran to look like himself. Maybe it doesn't manifest in a seven-inning shutout, but landing more pitches for strikes and staying a bit further away from hard contact are musts for Kelly.