The tentative 2026 Opening Day rotation for the Diamondbacks is set to look very much the same compared to 2025. Arizona reportedly re-signed Zac Gallen to a one-year deal, as the right-hander will look to rebound after a down 2025 season.
A Look at Gallen
Heading into a contract year, Zac Gallen had a tough season. Across 33 starts, Gallen posted a 4.83 ERA and gave up a career-high 31 home runs last season. His 1.45 HR/9 ranked in the bottom 30 among starters (min. 100 IP). It was a stark contrast from the rest of his career, as Gallen posted a 4.00+ ERA just once more in his career (2021).
His .315 opponents’ wOBA ranked 75th out of the 126 starters who threw at least 100 innings last season.
For Gallen, the game isn’t necessarily about swing-and-miss. The 30-year-old has never been an elite swing-and-miss pitcher. Rather, it’s more about changing looks and getting hitters off the fastball.
Over the last three seasons, Gallen had 983 called strikes off the fastball, second-most in the Majors, and it wasn’t particularly close. Jack Flaherty was third with 820, while Kevin Gausman was the only one ahead of him with 1,077.
His fastball is a riser with cut — and one that hitters don’t pick up all the time. That pitch is his true ace-pitch. Aside from that pitch, Gallen uses his signature curveball, which goes along with his cutter, changeup, slider, and sinker.
Looking back at Gallen’s pitch usage month-to-month, it illustrates the back-and-forth that he had with his arsenal. As you’ll see throughout the year, the fastball was used fewer and fewer, while Gallen ticked up the usage of his changeup, really started to use the two-seamer around midseason, and dialed back the cutter somewhat.
Gallen had more success throughout the year with the changeup, which was a swing-and-miss pitch. The 30-year-old saw a dip in swing-and-miss off the fastball between July and August, and that slowly ticked up in the final month with the increased usage of the changeup.
| Month | Whiff% |
|---|---|
| July | 23.3% |
| August | 28.9% |
| September | 34.4% |
Additionally, Gallen’s cutter, despite being scarcely used, was hit hard in 2025. Five home runs were off that pitch.
Per the New York Times, the Diamondbacks will give Zac Gallen a one-year deal worth $22MM.
Analysis
The qualifying offer for the 2025-26 offseason was $22.05MM, meaning Gallen made back what he rejected in November when Arizona gave him the qualifying offer. And, it’ll mean Gallen can go back to market this coming November with no draft pick compensation attached.
For the Diamondbacks, the move deepens a rotation that’ll tentatively include Merrill Kelly, who also re-signed with the team, Brandon Pfaadt, Eduardo Rodriguez, and Ryne Nelson, with Corbin Burnes looking to come back later in the season.
But for Gallen, it’ll give him a chance to rebound after what was a down 2025 season. You can slice his numbers anyway which way possible but it doesn’t change the fact that Gallen gave up more contact in 2023 and 2025 than he did in all of the seasons he’s pitched in the Majors.
Now, Gallen has a chance to get back on track, and with a Diamondbacks team that has expectations yet again in 2025. The Diamondbacks, despite losing Corbin Carroll to a hamate bone fracture, still have a premier offense, thanks to Carroll, Ketel Marte, Geraldo Perdomo, and Nolan Arenado, the latter of whom will look to get back on track in the desert.
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