A significant improvement was predicted.
Predictions can be quick and simple. Let’s look at Diamondbacks pitching in 2025 and predict runs allowed.
Starting point. Let’s assume that the Diamondbacks team will face same number of batters as last season.
Let’s divide the pitchers into two groups – the 12 with the most innings and the rest of the pitchers. That is meaningful because every season the 12 with the most innings have significantly less runs allowed per batter faced. Please keep in mind that the top 12 includes some (not all) starters and some relievers.
Baseline Runs Allowed.
Instead of a focus on ERAs and innings pitched, let’s focus on runs allowed per batter faced. A baseline of runs for each group can determined by calculation: batters faced multiplied by the Diamondbacks runs-per-batter-faced for that group in 2024.
- Top 12 pitchers, 577 runs allowed
- The rest, 211 runs allowed
Adjustments to the baseline.
To improve the prediction, adjustments need to be made for a few specific pitchers.
Corbin Burnes was acquired. Assuming he pitches as well as last season, he will make an impact by pitching games in place of pitchers who are less skilled. That will conservatively result in 18.7 less runs allowed.
My view is that Brandon Pfaadt will pitch better (based on his FIP and other indications). His runs per batter faced will improve to last season’s average of the top 12 pitchers. That will result in 11.2 less runs allowed.
Eduardo Rodriquez will return healthy, with better results, and face more batters than last season (conservatively, 430 batters faced is the average of the last two seasons in AAA and the Majors). That will result in 3.7 less runs allowed.
I hope not, but A.J. Puk might regress a little from his most excellent performance as a Diamondback. Perhaps that regression will be as much as from .039 to .078 runs-per-batter-faced (which is better than .086 projected by ZiPS DC). However, he will face more batters so that overall he makes a positive impact (perhaps 4.4 less runs allowed) on the team’s average runs-per-batter-faced. His success as a high leverage pitcher means his impact on wins will exceed his impact on runs allowed. As a Diamondback, last season he was a top-6 reliever in the Majors based on the following statistics (minimum 20 innings pitched, data from Baseball Reference):
- 1.63 FIP, second best reliever in the Majors.
- 322 ERA+, fifth best reliever in the Majors.
- 0.732 WHIP, fifth best reliever in the Majors.
- 14.2 SO/9, sixth best reliever in the Majors.
Jordan Montgomery is a wild card. This season, will he pitch better? Will he move to long relief in the bullpen? Will the Diamondbacks trade him? If he pitches surprisingly well, will the Diamondbacks keep him or trade him? And how many innings will he pitch for the Diamondbacks? If he improved to last season’s average runs-per-batter-faced of the top 12 pitchers that would be 18.7 less runs allowed compared to last season (assuming he faced the same number of batters).
Better pitching by the top 12 pitchers will reduce 788 baseline runs allowed to 731.3 runs allowed.
Outside the top 12 pitchers, impacts will happen. The following could have positive impact:
- Seth Martinez was acquired. He’s been called a late bloomer. He will very likely shine as a Diamondback. For details, see this AZ Snake Pit article.
- Drey Jameson will return from Tommy John surgery. In 2023, his 16% whiffs, and 40% shutdowns were impressive. That compared to a low 7% meltdowns. Although his innings will be limited, more likely than not he will make a positive impact. For comparison of relief pitchers, see this AZ Snake Pit article.
- Last season, Cristian Mena started one game. Despite having 3 great pitches (in a 5-pitch mix), he was not ready. Based on his 11 great starts in AAA Reno, it will be surprising if he has not started a game by the end of the season.
[Cristian Mena:] “He’s a big, strong kid and should be durable enough to be a 180-inning guy if he can find a way to get left-handed batters out enough to stay in a rotation.” — Keith Law February 2025
- Tommy Henry is on the 40-man roster. At 27.5 years old, he is the oldest Diamondbacks pitcher that Roster Resource shows in the minors. Perhaps he will be called up and make an impact as a reliever.
It’s very likely that other pitchers (don’t yet know who) will be disappointing. For predicting team runs allowed by pitchers outside the top 12, my initial assumption was that the positive impacts will be cancelled out by the negative impacts.
Then, Kendall Graveman was acquired. In 2023, his 4-seam fastball’s .200 wOBA was much better than league average. Overall, his .096 runs per batter faced, and the intangible benefit of possibly closing, will likely make a big impact. The overall positive impact will be 10 less runs allowed.
Data from Baseball Reference, FanGraphs, and Baseball Savant.
The mix of pitchers will have an impact.
What percentage of batters will the top 12 pitchers face? In 2023 it was 78.4%. In 2024 it was 77.1%. The FanGraphs DC ZiPS projection was 73%, perhaps because the Diamondbacks have great depth in starting pitchers. On the other hand, this season will have likely experience reduced injuries compared to last season, so 78% could happen. Let’s look at 73%, 77.1%, and 78%
- 73%, 728.6 runs allowed.
- 77.1%, 721.3 runs allowed
- 78%, 720.1 runs allowed.
Better outfield defense will have an impact.
Last season in center field, the Diamondbacks had negative 11 Defensive Runs Saved (DRS) per The Fielding Bible. Perhaps the biggest cause was Alek Thomas injured his hamstring which impacted his DRS in center field, which fell from positive 5 (in 2023) to negative 1 (in 2024). Furthermore, Corbin Carroll, who played roughly half his innings in center field where his DRS was negative 6, was at his best in right field (where his DRS was positive 3). A healthy Alek Thomas and a healthy Corbin Caroll will likely result in 16 less runs scored.
“My vision for the outfield is to have an elite defensive outfield. We have had that, and I think it makes a huge difference for the pitching staff.” — Mike Hazen, February 2025
Summary.
Last season, the Diamondbacks allowed 788 runs, ranking 26th in the Majors.
This season, the rounded prediction is between 704 and 713 runs allowed. If the prediction is accurate, the Diamondbacks runs allowed will be near the league average (which was 711 runs allowed). It’s a significant improvement! The improvement matches my common sense perception of the situation.