Projecting a Diamondbacks Rotation Without Corbin Burnes

As most followers of the Arizona Diamondbacks, and MLB in general, are aware by now, ace starting pitcher Corbin Burnes will undergo season-ending Tommy John surgery next week, and will be out until at least late summer 2026.

While it's a devastating blow to Arizona, the season marches on. The D-backs are not the only team to sustain major injuries to key players. Dealing with these types of situations are part and parcel of being a major league organization. The question is whether or not the D-backs have the depth with absorb this injury and sustain a competitive run without Burnes.

It should be noted that despite Burnes' excellent 2.66 ERA in 12 starts, the D-backs rotation has been a major disappointment. The team's starting pitcher's ERA is 4.43, which ranks 24th in MLB.

There have been plenty of surprisingly poor performances. Zac Gallen, Eduardo Rodriguez, and Brandon Pfaadt all have inflated ERAs, offsetting the work of Burnes, Merrill Kelly, and Ryne Nelson who have all been much better than average.

What follows is a quick examination of the pitching projections for the starting pitchers for the rest of the season. These come from Fangraphs Depth Chart rest-of-season projections, which are derived from the average of ZiPS and Steamer projections. As we all know, projections are simply a useful data point that can help baseline future expectations. They are not predictions.

Below, the projections look at the rest of the season for the five main starting pitchers. Note this totals 86 of the remaining 99 starts. The other 13 are projected by FanGraphs to be divided up between Bryce Jarvis, Cristian Mena, Tommy Henry, Yilber Diaz, and Drey Jameson. That is a stab in the dark on their part, as it's impossible to predict how the team will react to future injuries or poor performance from current rotation members.

Also note we are showing the FIP, or Fielding Independent Pitching. This is a peripheral-dependent metric based on the things the pitcher has more control over, i.e. walks, strikeouts, and home runs.

Diamondbacks Starting Pitchers Projections | Jack Sommers

Somewhat encouragingly, the projections see roughly a league average ERA from the starters the rest of the way. The league average showing in the table is the projected ERA for all pitchers, starters and relievers for the rest of the season. The actual starting pitcher's average ERA is 4.02. Bottom line, the D-backs are projected to have average starting pitching the rest of the way.

That may seem like a fairy tale to some, considering what we've seen so far, on top of the loss of Burnes. But it's important to remember that we are still only 63 games into the season, and the individual sample size for the season thus far is not very large in statistical terms. The projections consider previous track record, with more recent performance being weighted more heavily however, so year-to-date performance has impacted rest-of-season projections.

Zac Gallen was the former ace of the staff before the Burnes signing. He came into 2025 with a 3.45 career ERA and a projection for a 3.69 ERA for 2025. That projection already accounted for his more recent performance. He currently has a 5.13 ERA in 13 starts, 73.2 innings, however. His rest-of-season ERA has bounced up to 3.91 as a result. He'll need to step up to meet that modest number, and the team really needs him to do more.

Merrill Kelly entered the season with a career 3.82 ERA and 4.04 FIP. His 2025 projection was for a 4.03 ERA. He's beat that so far, with a 3.43 ERA, and his rest-of-season projection has improved to 3.89 as a result.

Brandon Pfaadt began 2025 with a 5.06 ERA but a 4.15 FIP. That nearly one-run gap suggested that Pfaadt was pitching better than the results he had gotten. His 2025 preseason projection was for a 3.88 ERA and 3.73 FIP. Those projections have wildly missed the mark so far, as he's posted 5.51 ERA and 4.91 FIP. Pfaadt has allowed 14 runs in his last three innings pitched.

Eduardo Rodriguez entered 2025 with a career 4.08 ERA and 3.89 FIP. His ERA projection for 2025 saw something closer to his FIP, coming in at 3.84. After throwing five innings and allowing two runs in a rain shortened game Friday night, his ERA dropped to 6.70 while his FIP is 4.30. Rodriguez is a case where bad luck has been a factor, but even if his ERA matched his FIP, he'd be half a run higher than his projection. Still, there should be some encouragement going forward.

Ryne Nelson had a career 4.57 ERA and 4.34 FIP at the start of 2025. Thanks to posting a 3.02 ERA from July 2 onwards last year, his ERA projection thus came in 4.03 and 4.14 respectively. He's continued to beat those expectation. Nelson has posted 3.43 ERA and 3.27 FIP in a hybrid long reliever/spot starter's role. In his three starts he has a 1.69 ERA.

Summary

As stated, projections are not predictions and should not be treated as such. But the takeaway here is that the above five pitchers producing a cumulative league average ERA is a reasonable expectation.

That expectation does not account for at least a dozen starts that will end up going to pitchers further down the depth chart however. The D-backs are going to need to be fortunate with health for the above five going forward, and hope that performance for Gallen, Pfaadt, and Rodriguez stabilize to something close to the projections.

Arizona has the fourth-best offense in all of MLB. If they can pair at least a league average rotation with that, and the bullpen continues to stabilize (that's a separate article), then the playoffs are still within reach. There is plenty of uncertainty around all of this, but they're still in it with 99 games to go.

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