What Does the Optimal San Diego Padres Bullpen Look Like?

[Randy Holt]

The most shocking component of this year's trade deadline wasn't so much that A.J. Preller and the San Diego Padres traded for one of the best players believed to be available. It was that they traded for one of the best players believed to be available at a position that didn't represent a present, on-paper need. In acquiring Mason Miller, the Padres further enhanced the strongest part of their roster. It's a relief corps that ranks at the top of the league in fWAR (6.2), ERA (3.06), and FIP (3.48) while ranking fourth in strikeouts (24.5 K%) and hard hit rate against (37.5 percent).

While somewhat puzzling at first, there's no shortage of merit in such a deal when you consider the idea that Robert Suárez will likely opt out of his contract to hit free agency after the season. Preller was able to gain some medium-term stability at the back of the bullpen (with Miller serving as the future closer) while simultaneously giving the Padres as strong a relief group as exists in baseball. It's the sort of roster component that really fortifies your team in matters of postseason baseball, especially when you consider some of the longevity issues that the team has faced out of the rotation.

The Padres certainly find themselves well-positioned for such an environment. As of this writing, they're just two games back of the Los Angeles Dodgers in the National League West and three games clear of the New York Mets in occupying the No. 2 wild card slot in the NL. Something rather catastrophic would have to unfold at this rate for the Padres not to be playing October baseball. 

But in matters of the bullpen, what happens when they get there? We know the shape that it's taken thus far since the deadline, but is there a specific way in which Mike Shildt can optimize his elite group of relievers in order to maximize the outcomes? 

This is, of course, specifically in reference for the "closing out games" aspect of relief work. With such a high volume of effective arms coming out of the bullpen, you're unlikely to see names like Yuki Matsui or Wandy Peralta getting into the late-inning mix. They're strictly bridge guys or arms you deploy with a large lead or deficit at this point. 

It's also difficult to include David Morgan in such a discussion. He's been excellent, pitching to a 1.57 ERA and a 26.0 percent strikeout rate across 25 games courtesy of his 97th percentile fastball velocity playing off strong curveball and slider offerings (123 and 122 Stuff+, respectively). But you also have to figure that with five arms in possession of more experience in late-game situations, he's going to end up falling into that same mix with Matsui & Peralta when the rubber meets the road, even if he presents more upside than either of the other two. 

Which leaves us with five: Suárez, Miller, Adrián Morejón, Jason Adam, and Jeremiah Estrada. With that group, you're getting the following: 

• Suárez: 3.28 ERA, 26.2 K%, 7.2 BB%, 67.7 LOB%, 33.3 GB%, 1.9 fWAR
• Miller: 3.80 ERA, 40.5 K%, 11.9 BB%, 69.2 LOB%, 36.4 GB%, 1.0 fWAR
• Morejón: 2.00 ERA, 25.7 K%, 5.2 BB%, 65.0 LOB%, 53.2 GB%, 2.0 fWAR
• Adam: 1.73 ERA, 26.3 K%, 10.4 BB%, 84.1 LOB%, 43.5 GB%, 1.0 fWAR
• Estrada: 2.52 ERA, 36.3 K%, 7.9 BB%, 77.6 LOB%, 38.3 GB%, 1.6 fWAR

In broad strokes, the Padres have a quintet of five power arms at the back of their bullpen. But, what's genuinely interesting about this group is that they also represent five distinctly different type of pitchers. Four of these five, along with Morgan, make up the top five in average fastball velocity on the Padres' pitching staff. Miller, of course, leads the way (102.1 MPH on average), followed by Suárez (98.5), Estrada (97.9), Morejón (96.7), and then Adam follows a little bit lower on the list (94.5). 

What separates them is in their secondary offerings. Miller & Morejón are each heavy on the slider. For Suárez, it's the changeup. Estrada brings his variation of a splitter and the occasional slide piece. Adam deploys his slider and change more than his fastball. It's a lot of velocity and a lot of movement. 

So, what does the optimum distribution of time look like? 

Lucky for us, Statcast can not only isolate each pitcher's performance into run value but add in a leverage factor. That leaves us with the following: 

While it doesn't have the ability to distinguish starter from reliever, it does speak to the strength of our group of focus that each of the possible late-inning arms falls inside of the team's top eight pitchers in run value. And if we're going by this alone, which factors in leverage, Morejón would be the guy to get the highest of leverage spots (i.e. the ninth inning). That would leave Estrada & Adam for eighth inning work and Suárez & Miller for the seventh. Again, that's if we were going purely based on run value, which, of course, is not the case. 

In terms of actual structure, we know that Suárez is going to get the ninth. Even with Miller's arrival, the veteran closer has continued to get the ninth inning work, so we have to assume he's locked in from here until his (assumed) free agency. But what about the rest? 

The massive benefit of running such a deep 'pen is that Mike Shildt can play the matchups to his liking as much as possible. So, for a lefty-heavy lineup (like a certain team within the Padres' division), you're quite obviously going to get Morejón involved in the late-going, as he's allowing a .154 wOBA against hitters of the same handedness. Interestingly, the other option for a late-inning situation would be Estrada, who has demonstrated some notable reverse splits in 2025 (.223 wOBA vs. lefties & .273 wOBA against righties). 

Miller represents the antithesis of Estrada, as he's struggled quite a bit against left-handed hitters this year. They've gone for a .347 wOBA versus the fireballer, as opposed to a .204 mark from right-handed hitters. With some of the command issues that Miller has been prone to, you're likely avoiding lefties at all costs for Miller when the bullpen is in action.

Adam is a relatively unique quantity among this group, as he's remained relatively split-neutral this year. Left-handed bats have a .264 wOBA against Adam while righty hitters are at .261. He gives you an option to go against either handedness, but perhaps a bit lower on the depth chart when lefties are involved given the run values of each of Morejón and Estrada in comparison to himself. 

If you wanted to pinpoint the ideal order, you're looking at Adam in the seventh given his versatility, with each of Morejón, Estrada, and Miller getting work in the eighth depending on handedness. Suárez remains the guy in the ninth, even if the numbers don't love him against his counterparts. But, when you're talking about five different pitchers (to say nothing of David Morgan), there are myriad combinations that would conceivably work when games progress into those high leverage moments.

Regardless of the form it takes, though, A.J. Preller has built something rather remarkable with this San Diego relief corps. There is so much velocity and so much movement that he's fortified a pitching staff that was subject to questions given inconsistency out of the starting gate. It relieves quite a bit of pressure from the starting staff to work deep into games when that might simply not be in the cards for this particular group.

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