After hopeful signs in 2023, this year was a reversion to form
Back in May 2023, I looked at the struggles of the Diamondbacks bullpen during the time of Mike Hazen as GM. At that point, the team has been below average in the “holy trinity” of pitching metrics – ERA, FIP and xFIP – every year since 2019, but there was some reason for hope, with an xFIP which, at the time, ranked a respectable twelfth for the season by xFIP. Unfortunately, results the rest of the season did not go the D-backs’ way. They ended the year in the bottom half there, in seventeenth place. And that was better than they managed by ERA (18th), FIP (21st) or fWAR (24th). However, that was still an improvement, considering they were dead-last by fWAR in both 2022 and 2023.
Indeed, while still below average across the board, it was more or less the best result by every metric for the Arizona bullpen since 2019. D-backs relievers had a 2.31 ERA in September 2023, and carried that into a strong post-season performance. They did not allow a run over 9.1 innings in the Wild-Card series, and through the end of the Championship Series, had a 2.92 post-season ERA, facing some of the strongest offenses in the majors. While they did run out of gas in the World Series, mostly due to Paul Sewald giving up six earned runs in two innings, there was hope that Hazen had finally cracked the bullpen code, and could assemble a solid set of relievers for the 2024 campaign.
Unfortunately, that did not turn out to be the case, with the Diamondbacks’ bullpen regressing back into the bottom third. Here’s where they ranked in 2024, along with an updated version of the graph from the previous article, now including the final numbers from 2023 and 2024.
- ERA: 4.41, 25th
- FIP: 4.19, 25th
- xFIP: 4.13, 21st
- fWAR: 2.3, 22nd
I guess the best thing you can say about the 2024 bullpen is, it wasn’t as flat-out terrible as the 2021-22 versions. But there was still an awful lot of room for improvement and a great deal of wasted resources. The trio of Sewald, Miguel Castro and Scott McGough, for example, combined to be paid $15.35 million. But through injury and ineffectiveness, they pitched a total of only 86 major-league innings between them this year, with an ERA of 5.76. This follows in the footsteps of other well-paid, underachieving relievers in the Hazen era. The most obvious is Mark Melancon, who was paid $12 million to throw 56 innings and post a 3-10 record along with an ERA of 4.66.
This may not be an issue in 2025. All three of the above relievers are free-agents this winter, and the most expensive bullpen arm right now for Arizona is projected to be Ryan Thompon. He’s expected to come in at $2.9 million, below the relatively restrained $3m cost of McGough. A.J. Puk, Kevin Ginkel, Joe Mantiply and Justin Martinez will be less still, and offer a range of options as possible closers. I can see a scenario where Hazen doesn’t splash big in the open market, needing to use the available resources to fill the gaps on the hitting side, left by the departures of Christian Walker, Joc Pederson and Randall Grichuk as free-agents.
Will the bullpen be any better in 2025? That’s less certain, because part of the problem in 2024 was the long tail. Martinez, Ginkel and Thompson all threw over 60 innings each. Between them and mid-season arrival Puk. the D-backs got 236.1 innings at an ERA of 2.78. Excellent. The problem is, there were 380.2 other innings pitched in relief by 23 further Arizona relievers. Even if we discount the work of Tucker Barnhart and Pavin Smith in mop-up duty, the rest of the bullpen still had an ERA of 5.40. There weren’t all low-leverage work either, with those “rump relievers” notching fifteen losses and seeing about half of all plate appearances classed as ‘High Leverage’ by Baseball Reference.
Nice though it would be if we could roll out just the good guys, the reality is, bullpen depth is increasingly important. When the D-backs arrived, relievers tossed less than fourteen thousand innings per year. Since the pandemic, the average is nearly eighteen thousand. One extra spot, which may or may not go to the bullpen, doesn’t balance that. Arizona starters averaged only 5.10 innings per game last year, and games can be lost just as easily in the sixth inning as the ninth. Through five innings this year, more than half the games (89) had a margin of two runs or fewer. Discounting the tied games, twenty of them saw the final result reversed from the situation at that point. So all bullpen arms matter, as it were.
That’s even discounting the inevitable attrition through health. We had nine different guys throw at least 20 innings in relief this year, and Arizona hasn’t had fewer than that since 2007. With the departures noted above, it’s going to be interesting to see how Hazen configures the rest of the bullpen spots. There are plenty of internal options: most of the 21 rump relievers are still under team control for 2026. But are there any of them about whom you feel confident? While a small sample size, Joe Mantiply and Humberto Castellanos were the only ones with a FIP below 4.30 in 2024. We may see more trawling of the waiver wire and DFAs, where Thompson was found.
While attention this winter will likely be focused on replacing the likes of Walker and Pederson, the small margin by which Arizona missed out this year emphasized how every loss matters. Getting a bullpen simply to league average – a modest enough ambition – would have likely made the difference in 2024. In general, teams are better off addressing the low-hanging fruit if they want to improve. Over the past five years, with Arizona having the worst bullpen in the majors by fWAR, barely above replacement level, our relievers have positively been brushing against the ground. Maybe 2025 will be the season Hazen finally cracks the bullpen code.