It’s well known that relievers are a volatile bunch. From year to year you don’t usually know quite what to expect, as mediocre relievers suddenly blossom and have career years and the guys you thought you could count on inexplicably struggle.
Sometimes this volatility doesn’t just show up from one season to the next. Relievers often have great months followed by terrible months even though their velocity and arsenal remain unchanged. Case in point, Justin Sterner, April 2025: 14.2 IP, 0 ER. May, 2025: 11.2 IP, 9 ER. September, 2025: 12 IP, 1 ER.
This makes it especially hard to construct a bullpen for an upcoming season, not knowing who will regress or blossom for no apparent reason, and who will pitch with at least some consistency from month to month versus who will ride the proverbial roller coaster.
Why are relievers so prone to this extreme variance? Some possible answers:
They’re Not
Perhaps relievers aren’t that much more volatile from season to season and month to month than other players. Cody Bellinger is a good example of a position player who has vacillated from spectacular to spectacularly awful without warning. In 2025 Cam Smith went from a 116 wRC+ in the first half to a 41 wRC+ in the 2nd half. Is the whole ‘relievers are volatile’ narrative a “perception” thing rather than a reality?
Small Samples Produce Large Variance
Relievers don’t wind up accruing large inning totals and anytime you look at 50 inning samples instead of 150 innings or 500 plate appearances, you are going to see more variance. This is especially true the more you zoom in: the samples cited above for Sterner are all of 11.2 – 14.2 innings each.
Perhaps the difference between a good season and a medium season, at least statistically, boils down to 2-3 gascan appearances totaling 3 IP and 8 ER which inflate the numbers in a 50 inning sample. A starting pitcher with one start out of 30 in which he lasts just 3 innings and serves up 8 ER still has a chance to put up excellent overall numbers.
It’s The Demographic, Stupid
Hey, no insults on AN please. OK I suppose it’s fine to insult yourself. Just don’t do it again, dumba$$. Anyhoo, another theory is that who becomes a reliever is not a random group of pitchers. It’s pitchers who specifically did not make it as a starting pitcher and don’t have the stuff to thrive multiple times through a batting order.
This might mean reliance on 2 pitches, in which case any time one pitch isn’t working you have a “one pitch pitcher” on your hands. Or it might mean not being good enough to crack the “best 5” — including the flaw of not being consistent enough from outing to outing, or from inning to inning.
Perhaps what got a reliever to the bullpen is precisely what makes him more prone to volatility: he has the stuff to pitch in the big leagues, but just enough flaws to require a slot in the bullpen rather than the rotation.
There’s 3 possibilities, any or all of which could be right or wrong. Here’s where you come in (to type a minimum of 3 words, new rules) and weigh in on whether any of these are correct or what other factors might be in play. And if you have truly figured it out, by all means share it with the A’s because I can assure you no one in MLB has all the answers — or relievers would be a lot more consistent and bullpens would be much easier to assemble.
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