The evolution of Eduardo Rodriguez: How the D-backs left-hander reshaped his arsenal

It takes more than just a big-league fastball to survive in today’s analytical landscape. As hitters gather more data, pitchers are forced to adapt, find new ways to disrupt timing and keep opponents guessing.

For the Arizona Diamondbacks, look no further than Eduardo Rodriguez’s recent transition on the mound.

Once heavily reliant on his high-velocity heater, Rodriguez has drastically altered his approach, leaning into a more complete mix that is keeping hitters off-balance.

“He’s evolved as a pitcher,” D-backs GM Mike Hazen said during an appearance on Arizona Sports‘ Wolf & Luke on Wednesday. “He’s using all of his stuff. He was very heavy fastball-dominant. He’s always had a really good fastball. He was throwing his fastball way too much in the past. He’s now mixing all of his stuff. That mix is creating uncertainty for the hitters.”

By Eduardo Rodriguez’s numbers: shifting the arsenal

The data backs up the eye test. After years of relying heavily on his raw heater, Rodriguez’s four-seam fastball usage has plummeted to 39.7%, it’s lowest frequency since 2022 and the fourth lowest of his career.

Instead, a renewed emphasis on his secondary offerings, most notably his curveball, has filled the gap. The addition of the breaking ball has completely altered how hitters approach him.

His curveball is at 12.9% this season, while Rodriguez has only thrown it enough to register in two other seasons: 2025 (4.7%) and 2019 (3.2%).

“He’s mixing in a curveball now, which he wasn’t doing in the past,” Hazen said. “All of those things that are setting off the hitters’ timing or their ability to sit on a particular pitch is creating more doubt, and that’s the whole game for pitching if you’re not Jacob Misiorowski. The whole game is creating doubt for the hitter so they can’t just sit on something. He’s done a much better job of that.”

The “Merrill Kelly” blueprint

Hazen drew a direct parallel between Rodriguez and veteran teammate Merrill Kelly, who built his career on mixing speeds, hitting spots and staying composed under pressure.

“It’s not perfect, he doesn’t strike out 10 guys a night,” Hazen said of Rodriguez. “It’s not raw, blow-you-away with stuff. But it’s in the evolution of some of these guys, Merrill Kelly’s another example of this. As they get older, their advantage is their ability to pitch, throw multiple pitches, command their stuff, not get rattled when you got first and third with nobody out, that’s the separator skill. And you have to use it to your advantage, I think he’s doing that more.”

In an era of advanced scouting reports and instant video access, static repertoires quickly get exposed. Hitters are simply too smart, making evolution a necessity for survival rather than a choice.

“I think as these guys that don’t have pure stuff to blow hitters away, as they get older, they continually need to evolve to keep the hitters off balance,” Hazen said. “These guys in the league know everything about everybody now. You’re not sneaking up on anybody, so now it becomes creating the best mix you can.”

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