A 4.50 ERA is never going to jump off the page at you. It’s pretty average production for a pitcher and in some circles, considered below average. That’s Aaron Bummer’s ERA through the first 5 weeks of the season, and so it’s easy to conclude Aaron Bummer has been an average relief pitchers so far 2024. Or even below average.
I don’t think either has been the case. Has he been elite, no. But I think he’s been better than the general fanbase thinks.
The easiest way to show this is to point out that 4.50 ERA is accompanied by a 2.81 FIP, a 2.31 xFIP, a K/9 of almost 10 and a BB/9 of 2. Those are all fantastic peripherals, and all point to the conclusion that Bummer is experiencing a common occurrence where results early in a baseball season don’t align with the process that’s went into them, leading to some unfortunate mischaracterizations. See “AJ Minter, April 2023” for further reading into the subject.
And it’s not hard to see where some wonky stuff has been happening. Bummer has induced a 60% ground-ball rate so far in 2024, an elite number and one that should lead to favorable results for any pitcher. For the season, the league-wide batting average on grounders is .239. Not at all surprising, hitting the ball on the ground is a tough way to make a living for any offensive player. But when Bummer has induced a ground-ball this season, the batting average against him is .409. The league-wide wOBA for grounders this season is .223. The wOBA against Aaron Bummer grounders so far this season is .366. Those are massive gaps and there’s no chance that’s going to last. The league is not going to continue to have elite levels of production on ground balls against Bummer while the league-wide numbers are so putrid. This is small sample size theatre at its finest.
It should be pointed out, Bummer hasn’t been completely blameless in this. The average exit velocity on his grounders this season is 91.1 mph, a very high number and 6 mph above the league average number for ground balls. But even 91 mph ground-balls shouldn’t be producing a .409 batting average and a .366 wOBA. He’s had a few that, yes were hit hard, but hit straight down into the ground and with better luck, should’ve been outs.
This ball was hit 103 mph but you wouldn’t know it because it was hit at -20 degrees launch angle and just so happened to be hit where no one was standing:
