Why Aaron Bummer is a great fit for the Braves bullpen and roster

The trade surprised a lot of people, but similar to Pierce Johnson, there's reason to believe a new environment will work wonders

The Atlanta Braves pulled off the biggest trade (so far) of the offseason late last night, acquiring lefty reliever Aaron Bummer from the Chicago White Sox for a five-player package of mostly non-tender candidates and non-contributing players for 2024. 

Atlanta Braves trade five player package for reliever Aaron Bummer from Chicago White Sox

Here's some thoughts as to why the trade's a much better deal than initial impressions would lead to believe. 

Aaron Bummer could potentially be much better than he showed in Chicago

Kamil Krzaczynski-USA TODAY Sports

On the surface, Aaron Bummer's 2023 performance for the White Sox isn't very encouraging: A 5-5 record, 6.79 ERA, and -1 WAR. 

But similar to the acquisition of Pierce Johnson from the Colorado Rockies at last year's trade deadline, it's a deal that makes a lot of sense when you dive into the details. 

We talked about the spread between Spencer Strider's 3.86 ERA and 2.85 FIP - Fielding Independent Pitching - when discussing the Cy Young voting this season.  

Bummer's discrepancy is even more severe. 

His ERA was 6.79, but his FIP was 3.58, showing that he was absolutely FAILED by his defense on balls in play. 

(Reminder: Fielding Independent Pitching measures a pitcher's individual effectiveness because it looks at only things the pitcher can control - strikeouts, walks, hit-by-pitch, and home runs. Any ball that is put into the field of play - whether a hit or an out - is removed from the calculation, because the outcome of that batted ball was subject to the defense's actions, not the pitcher.)

The Chicago defense has one of the worst fielding percentages in all of baseball, at only .983, and was bottom six in double plays turned, with 117. (By contrast, Atlanta turned 134 double plays with a .986 fielding percentage, both above-average numbers). 

For an extreme ground ball pitcher, a bad defense is a death sentence. 

And Bummer's an extreme ground ball pitcher - his ground ball rate of 60.1% in 2023 was in the 97th percentile in all of baseball, and despite allowing plenty of hard-hit balls (44.6%), he had one of the lowest barrel rates in all of baseball because of all those ground balls, only 2.7% (99th percentile). 

And in previous years, when Chicago's had a decent defense, Bummer's ERA has matched: A 2.36 in 2022, a 3.51 in 2021, and a 2.13 in 2019. (He pitched only 9.1 innings in the abbreviated 2020 season). 

The trade package leaving frees up some money for Atlanta in 2024

Brad Penner-USA TODAY Sports

While giving up Nicky Lopez wasn't easy, it was a chance to financially save some money. With Lopez and Michael Soroka both being in arbitration and being estimated at a combined $7.9M, Atlanta's freed up some funds for free agency. 

With reports coming out that Atlanta's not only willing to exceed their current $22M/year largest contracts in free agency, as well as Atlanta's determination to add a frontline starter, any money saved is useful. 

And Lopez's defensive contributions, while useful, aren't necessarily worth $3.9M when you think about his status as a backup on a team that allows their position players to play as much as health permits. 

Atlanta will undoubtedly roll with Vaughn Grissom as a backup (and probably in a left field platoon, as well, to get his bat into the lineup) and count on health and potentially a veteran acquisition on a minor league deal for emergency infield depth were significant injuries to strike. 

Soroka was estimated to be receiving $3M in arbitration, and based on his results last season combined with his season ending early due to injury, there was no assurances that he was going to stick in the rotation this season. And at five years of service time, a player can refuse a minor league assignment and opt for free agency instead, so trading him to a team that can run him in the rotation all-season makes sense. 

Between these trades and Atlanta's option decisions from last week (declining Eddie Rosario's $9M option, most notably), the Braves have freed up almost $20M in payroll space for a splash in free agency. 

You also create several open 40-man roster spots with the deal

Brett Davis-USA TODAY Sports

By trading MLB-level talent, Atlanta's opened several 40-man roster spots with the deal. 

Lopez, Soroka, Shewmake, and Shuster were all on the 40-man roster. Subtracting them but adding Bummer brings the total to 37 spots, so now you'd have room for free agent signings. Atlanta could reasonably add a left fielder, a frontline starting pitcher, and a utility infielder without needing to DFA anyone else. 

You also bolster your lefty depth in the bullpen

Atlanta can now roll out multiple lefties on Opening Day with Bummer and AJ Minter. This gives you the depth to allow Dylan Lee (shoulder) and Tyler Matzek (Tommy John), who are both rehabbing from injuries, to work their way back into form before immediately being dropped into key situations. 

If everyone returns to health and effectiveness, Atlanta's left-handed bullpen depth should be some of the best it's had in a long time, with four different southpaws able to take the ball at any given moment in a ballgame. 

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