EN: A newly leaked evaluation of Aaron Bummer has stunned Braves fans as analysts unveil surprising details about his 2025 performance arc. Early notes suggest his impact might be far deeper than the box score reveals. The buzz across Atlanta is growing rapidly as insiders hint at a major turnaround.

Generally-speaking, I’m not a huge fan of reliever extensions and long-term contracts, unless you’re one of the tippy-top relievers in the game. They’re too volatile, and their lifespans in the game are too short.

but sometimes, you get a super cheap one that you can’t pass up, and the Chicago White Sox got one of those in Aaron Bummer, when they signed him to a 5-year, $16 million extension prior to the 2020 season. The contract was fairly even from year-to-year, and he made nearly $14 million through 2024 (the rest of the guarantee was for buyouts in 2025 and 2026). During that time, he produced about 3.5 wins. That’s not … a lot, but it’s worth the $14 million, and then some. (It’s worth noting that Bummer’s extension came when he would’ve been paid arbitration-eligible money, rather than free agent money, so the White Sox didn’t get a gigantic savings. Still, he was coming off 1.5 excellent seasons of relief, so you can see why they locked in his salary the way they did.)

With two team options clicking on at $7.25 million for 2025 and 2026, the Atlanta Braves restructured the contract with Bummer to guarantee him $13 million over those years. Bummer gave up some potential earnings for some security. In doing so, he also chained himself to a team that had seemingly little interest in using him in higher leverage, as befits his production.

How acquired

The Braves, just a little over two years ago, acquired Bummer in a mildly hilarious trade of five players – Michael Soroka, Jared Shuster, Nicky Lopez, Braden Shewmake, and Riley Gowens. There were … names in this trade, but Soroka was broken by then (sadface), Shuster was basically already deemed not good, and Shewmake’s early prospect luster was mostly gone.

The White Sox are a Bad(TM) organization, they apparently believed the 6.59 ERA in 2023, and they were essentially dumping the contract. Whoops.

What were the expectations?

Bummer went back to being a fantastic lefty reliever in 2024. He kept striking out batters at a good clip (28 percent), and he nearly halved his 2023 walk rate (7.4 percent, down from 13 percent), which was the main point of concern in 2023. And of course, he added in a nearly 60 percent groundball rate. He got 1.1 fWAR for his efforts, and it would’ve been higher had the Braves not decided that Bummer needed to toil in lower leverage for some reason. He had the eighth-highest average leverage when entering a game among 2024 relievers, despite the second-best FIP- and best xFIP-, giving him the third-most fWAR.

Basically every expected pitching metric clocked Bummer as a mid-to-upper 2.00 “true” ERA reliever. The 3.58 ERA is basically something I’m blaming on the defense (.386 BABIP). That’s enough to be worth about a win.

The Braves basically expected something similar, perhaps somewhat lower a la 0.7 WAR, but still in the “well above average reliever” range. He was their left-handed do-everything reliever, and do-everything included the very real possibility that he’d be banished to low leverage again for some reason.

2025 results

They weren’t as good. A 3.81 ERA was pretty indicative of his season, and he got about a half win of value. His overall line was a 90 ERA-, 87 FIP-, and 89 xFIP-. The Braves also didn’t even bother pretending he was going to be used in high leverage, as he had by far the lowest average leverage for any of their four relievers that completed 50 innings in 2025, was essentially tied with Enyel De Los Santos in type of usage despite the latter getting kicked off the roster, and only barely exceeded the average leverage of someone like Dylan Dodd. The Braves had 14 relievers throw ten or more innings for them in 2025, and only three (Scott Blewett, Austin Cox, and Dane Dunning) were using in an even greater proportion of mop-up situations than Bummer. He finished with 0.4 fWAR, which was okay, but also his lowest total when completing the lion’s share of a season in the majors.

You can see the downward trend below. 2024 …

2025 Atlanta Braves Player Review: Aaron Bummer

Then 2025 …

He was heavily used, netting 54 innings before landing on the Injured List with shoulder inflammation and then ultimately hitting the 60-day IL in mid-September.

Bummer kinda-sorta changed his pitch mix, adding a curveball-type pitch that was basically his pre-existing sweeper, but with more drop. It didn’t really have the desired effect, as hitters fared better against both the more-drop curve version and the less-drop sweeper version than 2024’s sweeper; his sinker command also got notably worse in 2025. Whether all of the regression came due to the change in his arsenal, shoulder issues that forced him out of action late in the year, or dejection from basically being a mop-up guy whose demotion to this status was wholly unwarranted, we’ll never know — but it’s in the books now, anyway.

What went right?

Ultimately, the results were okay. Basically everything backed up for various, but he still got a ton of groundballs (54 percent) along with missing enough bats to be effective.

We also had this nifty pick-off of Xavier Edwards on August 9th.

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And he snagged this comebacker against the Brewers.

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His highest WPA games were ones where he actually went multiple innings, though.

On April 22nd, he bridged the gap in a weird one where Scott Blewett took the start and made it to the 4th before surrendering a leadoff walk, and Bummer came in to finish the that in that inning and took a second inning, striking out three. He stuck around for the offense to turn a 2-0 deficit into a 4-2 lead, but the bullpen later … blew it such that the game turned into a blowout loss. Still, Bummer did well, albeit once again being used in a bizarre innings-eating role.

In his penultimate assistance on August 17th, he helped the Braves win one by bridging an Erick Fedde start. He wasn’t a sharp in that one, but he was ultimately effective.

What went wrong?

Everything honestly went the wrong direction for Bummer.

After his velocity dropped an mph in 2024, we didn’t really care because he was so effective. But his velocity dropped … gulp … two more mph in 2025, and that had a negative effect on his ability to miss bats.

That led to his stuff regressing across the board.

That didn’t help him miss bats.

The strikeout rate plummeted to 22 percent from 28 percent, and while groundballs have airways saved Bummer, that also decreases from 58-59 percent to 54 percent.

When all off these things regress, it’s not good. He stayed fairly effective, but he’ll need to improve in 2026. Or, if the Braves are committed to using him as a mop-up guy, then whatever.

Something getting a shoutout for “what went wrong?” was the Braves’ commitment to forcing him to eat innings while starting, as their rotation was getting decimated. On July 12, he started a game against the Cardinals and made his way through an inning, as his offense took a 3-0 lead against eventual Braves Erick Fedde. The Braves then left Bummer in to give the three runs right back, even letting him face the leadoff guy for a second time in the process. A few days before that, Bummer made it through two innings unscathed to start a game against the Orioles, striking out five in the process, but then was left in to allow two homers in the third inning, including one to a guy facing him the second time in three innings. Those two games were, in fact, his lowest-WPA outings of the year, showing the Braves’ commitment to making sure that Bummer did not help the team despite his ability to pitch pretty well.

And, sure, sometimes pitching to contact will result in unfortunate results like this walkoff single that’s an inning-ending double play if hit more closely to a fielder, but them’s the breaks. Bummer has largely thrived in his career with that profile, but the Braves just don’t seem to care from a usage perspective.

2026 outlook

When the Braves restructured Bummer’s contract, they put $9.5 million of the $13 million in 2026. They’ll certainly want more out of him next season. It’s kind of up to them to actually use him in situations where they can get more, though.

Steamer sees something in the middle of 2024 and 2025, which makes sense. Basically, he’s projected an above-average but not necessarily great reliever. Bummer is only 31 years old, so he’s not too old. Getting a half-win isn’t going to be sufficient to make up for the contract extension here, and Atlanta likely would have been better off keeping the contract as it was and potentially buying him out. But it’s not devastating enough to really argue about for much, especially when his usage is much more confounding.

There’s a decent chance of a Bummer Renaissance in 2026, something where he looks and produces more like his 2023 self, higher-leverage boost to his value and all. Such is the nature of relievers, including the fact that they get value boosts if they perform well in higher leverage.