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 RockiesMay 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 ImagesIn 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 continueApr 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