Del Castillo turns aggressive swing into lift as Merrill Kelly’s velocity jump sparks Diamondbacks win

The Arizona Diamondbacks’ July 5 victory did not hinge on one at-bat alone, but Del Castillo’s long ball and Merrill Kelly’s second-half adjustment gave the night a clear shape. The club paired a willingness to attack the strike zone with a starting pitcher who returned to a faster version of his repertoire, an approach that the Diamondbacks hope can translate into more consistent results as the season moves toward September.

Del Castillo supplied the game’s momentum swing with a home run that played as an exclamation point on Arizona’s emphasis early. According to the recap, Arizona’s hitting theme was simple: keep the pressure on, stay aggressive, and reward quality contact rather than waiting for the perfect pitch. While home runs are not always the deciding factor, they do tend to shorten innings and reduce the margin for error for the pitcher at the other end.

Kelly’s change looked physical first, then tactical. The report described him coming out “aggressive” and letting his pitches go, rather than aiming to be too fine or too precise. That mindset change showed up in the velocity data: each of Kelly’s six pitch types was above his season averages, with three of those types clocking more than 1.5 mph hotter than usual.

The Diamondbacks’ adjustment mattered because opponents had been “figuring out” Kelly’s approach, at least in his most recent starts. In the follow-up coverage, Kelly indicated that the league has been adjusting to what he has been doing and that he needed to adjust back. He tied the solution to establishing the fastball, noting that the rest of the plan tends to play off that pitch once it is a real weapon rather than a background element.

One concrete sign of that fastball-and-offspeed relationship was Kelly’s ability to miss bats with runners on. In the recap, he induced 13 whiffs in the start and finished with six strikeouts, tying a season high. The coverage also said those strikeouts helped keep the scoring down, particularly by limiting damage with runners in scoring position.

The Diamondbacks’ challenge now is making the “new look” repeatable. Velocity upticks can come and go, but the bigger test is whether Kelly can sustain the aggressive attack that produced the higher-powered pitch mix and whether Arizona’s offense can consistently translate that pressure into early innings and fewer high-leverage swings later. If Kelly’s fastball establishment continues, the Diamondbacks can better rely on his ability to shape counts and control the middle of an opposing lineup.

What to watch next is simple: whether Kelly’s pitch mix remains above his season baseline across subsequent starts, and whether Arizona’s hitters keep showing the same intent that framed this game. If those two elements hold together, this July 5 win can be more than a one-night turnaround, and instead become a template for how Arizona attacks from here.