If Brewers Need to Thin Herd in Bullpen to Make Way for New Talent, Who Should Go?

Back in March, Pat Murphy neatly articulated the important facets that make up bullpen construction in MLB right now.

"We want an advantage," Murphy said of the objective when selecting matchups late in games. "What happens is, you’re looking at more major-league bullpens right now [where] all the pitchers in the bullpen, with the exception of some lefties, they all can face both sides."

Murphy was talking about the ramifications not only of the three-batter minimum rule that has now been in place for half a decade in MLB, but about the slightly newer limits on the number of pitchers a team can carry, and about the creeping rise of volume teams must ask of their pens in an age of ever-shrinking starter workloads.

"You have only 13 pitchers, so the guys with options become crucial—and being able to bounce back, and be in the type of shape that you want to be in," he said then. "There’s all sorts of stuff at stake here."

As the Brewers wind down at the other end of a long season that bore out so much of what Murphy said, the truth of those statements is increasingly apparent. Flexibility is the name of the modern bullpen management game, and it takes many forms, from the ability to manipulate the roster to the ability to stick with a single pitcher through a pocket of the batting order containing varied hitters--and to the capacity to work on consecutive days, or three times in four, or across multiple up-downs within a game. Most of all, though, it's vital to seize a systemic advantage without needing it to be rooted in handedness.

"It’s the guys who have success on both sides; those are the guys that make it into the pen at the end," Murphy said. "You just can’t have a staff where a guy just can get out righties or get out lefties. You might be able to get away with one lefty like that, for a two out of three situation."

None of this much matters to the relief aces on the team. There's a threshold of sheer quality where ancillary concerns like durability, matchup vulnerability, and willingness to stretch beyond one inning per outing remain in the background. Devin Williams, Trevor Megill, and Joel Payamps all clear that bar with ease. For others, though, we do have to weigh these secondary indicators of fit and value, and they don't always come out positively.

Here's a chart showing all right-handed pitchers who faced at least 200 batters in the big leagues last season, with the percentage of those batter confrontations in which they had the platoon advantage as the independent variable and their opponents' weighted on-base average as the dependent one.

Obviously, the real dynamics aren't anywhere near that simple. The relationship between platoon advantage prevalence and overall performance is weak, not least because the best pitchers end up as starters and therefore face more opposite-handed batters. What it does tell us, though, is which pitchers were already being sheltered a bit by their employers. Thus, when we see Elvis Peguero and Bryse Wilson with well above-average platoon rates and subpar opponent wOBAs, the message is: these players were set up to succeed as well as practically possible, and they still didn't.

Peguero, as has been discussed on this site before, boasts reverse platoon splits, despite a pitch mix that wouldn't traditionally lend itself to them. Thus, you can argue that his usage is a reflection of misunderstanding the player the team had on hand and setting him up to fail, rather than of coddling him. Nonetheless, his results this season were discouraging. That goes even more strongly for Wilson, a pretty standard-issue righty whose chief virtue was durability and length, but whose performance degraded as the season wore on and who didn't benefit from getting to see a lot of righty batters, as one might have hoped.

Here's the same chart for left-handed pitchers.

Naturally, given how funky his delivery is and the superior stuff of the other two southpaws in the pen, Hoby Milner was the one most carefully deployed against lefty batters. However, his results were still noticeably worse than those of both Bryan Hudson and Jared Koenig. When the trend arrows on pitchers point in opposite directions, it can be tough to suss out the relative importance of each. With Wilson, Milner, and Peguero, though, their usage and their outcomes both seem to point the wrong way. They were given chances to establish consistency and reliability, and they didn't do so.

Milner and Wilson are arbitration-eligible, and MLB Trade Rumors projects them to earn a combined $4.2 million next season. Peguero isn't yet eligible, but he's now out of options. Reviewing the quotes from Murphy above and considering the seasons each of these three just had, it's not hard to argue that each could be replaced by players who can be deployed more flexibly and return greater value next season--at the same or lower total cost.

That's not to say that all three will or should be jettisoned this winter. It's unlikely, though, that all three make it through the offseason as part of the Brewers organization. As the Brewers weigh the talent, availability, and versatility of their in-house options; evaluate potential waiver claims and free-agent signees; and try to make room for incoming talent at higher-priority positions than relief pitcher, they're likely to move one or two of the three, be it by simply non-tendering them, waiving them to open roster space, or finding a new home for them via trade. It's a numbers game, and the numbers say these three are a bit less valuable than their rivals for roles on next year's pitching staff.