Diamondbacks Spring Questions: The Rotation

Seven into five won’t go

Will the Diamondbacks have the best pitching staff in the major leagues this year? That would seem to be a bold projection, considering they’ve had an ERA+ below 100 every year since 2019. and last year’s figure of 91 ranked Arizona 26th of the 30 major-league teams. But if ZiPS is to be believed, this season could be a historic one for Arizona. Here’s how its projections for 2025 stacked up, not long after the surprising signing of Corbin Burnes by the D-backs.

That 3.66 ERA, if achieved, would be the lowest ERA in the history of the D-backs, narrowly beating out the 3.67 figure from 2017 [though with a much higher run environment in those days, meaning the ERA+ of 128 that year was considerably better] If the team is to get there, the journey is going to start – and potentially finish – with the starting rotation. Right now, it seems almost overstuffed, with seven perfectly credible contenders on the roster. Perhaps the biggest question to be answered in spring training is, exactly how they are going to be fitted into the rotation for 2025. It’s quite possible the man who led the team in innings last year, could end up in Reno for Opening Day.

At the top of the depth chart, the only question with regard to Burnes, Zac Gallen and Merrill Kelly is likely to be, who will get to start on Opening Day against the Cubs? Zac has the advantages of incumbency and tenure. He will be going into his seventh season as a D-back, and received the honor in both 2023 and 2024. But Burnes also received the ball there, for Baltimore and Milwaukee – indeed, he was the Opening Day starter for the Brewers in 2022 as well. He will also be here for the long term, while this is currently Gallen’s final season under control by Arizona. If Burnes gets the nod, it might (or might not!) be a tacit sign the team is preparing to wave goodbye to Zac.

The fourth spot appears likely to belong to Eduardo Rodriguez, even though his first year for Arizona was definitely underwhelming. He made only ten appearances, the lowest figure in his career, and posted an ERA above five, barely better than replacement level (0.2 bWAR). Not exactly what you want for fourteen million dollars, in the first year of a four-year deal. This would likely have received considerably greater scrutiny, had it not been for an even more unimpressive debut, which we’ll get to. But Eduardo is going to have to do better: ZIPS thinks he will, projecting him for nineteen starts and a 3.68 ERA. That’s definitely going to help the team’s collective numbers.

The final spot is the fun one. At the time Burnes signed, the expectation was that the team would trade Montgomery for salary relief. However, here we are, pitchers and catchers reporting, and Jordan is still a Diamondback. Indeed the team’s payroll increased further with the signing of Kendall Graveman + Randal Grichuk. Though the structure of the latter, with the 2026 “mutual option”, basically defers cash without having to put it to one side, so minimizes impact on this year’s bill. It’s still possible Montgomery gets traded, especially as there will inevitably be pitchers on other teams who go down long-term between now and Opening Day. Desperation can be the mother of a successful trade, from our perspective.

Presuming that’s not the case, I would expect Montgomery to be in the rotation for Opening Day, despite being relegated to the bullpen down the stretch last season. He has shown up to training camp significantly lighter. Although surprisingly, Jordan does not feel like he is in a battle for a rotation spot, saying “I mean, that’s what I’m here for. They’re paying me a lot of money.” Admittedly, he’s not wrong. We’re not going to pay $22.5 million for a long reliever to throw mop-up. So if he’s here, it seems like a no-brainer that Montgomery will be in the rotation. If he can pitch to his ZIPS projections, of a 3.93 ERA, then that would be a damn good #5 starter for any rotation.

Indeed, the last time any National League team had five pitchers all make even 20 starts, with an ERA under four? That would be the 2021 Brewers, anchored by… yep, Corbin Burnes, who won 95 games and the NL Central. Up the qualifier to 25 starts, and it has bee done once in the past decade, by the 2016 Cubs, who won the World Series. Given good health and accurate ZIPS projections in terms of ERA, that’s the territory in which the D-backs could be operating this year. And that presumptive rotation doesn’t even include Brandon Pfaadt, projected for a 3.84 ERA, or Ryne Nelson, barely above the cutoff line at 4.01. Maybe the best pitching staff in MLB isn’t beyond the bounds of possibility.

This would leave the question of what to do with Pfaadt and Nelson, though again – we’re presuming none of the five men ahead of them get hurt before Opening Day. That’s probably more likely than not. Last year, we didn’t have our expected rotation of Gallen, Kelly, Rodriguez, Montgomery and Pfaadt, start five games in a row until the second half of August. Depth of starting pitchers is essential, and was one of Arizona’s problems last year. Though the speed and extent to which this was tested, was admittedly perhaps beyond the expected level. This year, we already have Montgomery being held back with a finger issue. Hopefully it won’t be serious. But see the “minimal” concern over E-Rod last spring…

Again, presuming perfect health, I think we’ll see Pfaadt go down to Reno. He can be kept stretched out there, as the first man up when (rather than if) a replacement starter is needed. Ryne could go down there too, but I suspect he might end up sticking around as a long man out of the bullpen. Especially until we’ve confirmed that Rodriguez and Montgomery can be relied upon to gets outs past the fifth inning. The schedule offers five days off before the end of April, which may inform the decision. I suspect the plan is already laid out, but there still six weeks until Opening Day, and so this is definitely a “card subject to change,” as they say in the wrestling world!