Atlanta's run differential tells a story about the 2025 season

The Atlanta Braves have underperformed in the win column based on their run scoring and prevention

The following newsletter is on request from premium subscriber Tom, after I solicited the private chat we have for newsletter topics they’d like to read about. Here’s his original comment:

I’m a big believer in run differential and it’s far enough along into the season to be relevant. The Braves (& Reds) are the underperformers in MLB. They’re the only teams with positive run differential and record below .500. Comparisons to some other teams are telling (Cleveland). What they’re “telling”, I’m not exactly sure. Attention to detail and good fundamentals? Would appreciate your perspective.

I can do that!

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It’s safe to argue that the Atlanta Braves have underperformed their potential this season.

Atlanta enters today’s series against the Philadelphia Phillies at 25-27, 3rd place in the National League East and the 5th team out of the NL Wild Card standings. But to Tom’s point, Atlanta is one of four teams that currently have a positive run differential despite being below .500.

In order of the run differential, as of Monday afternoon:

Cincinnati Reds, 27-28, +28
Boston Red Sox, 27-29, +17
Atlanta Braves, 25-27, +11
Arizona Diamondbacks, 26-27, +1

What can we learn from the positive-run-differential-but-losing-record thing? Let’s talk about it.

Is this actually statistically significant?

Especially as early as Memorial Day, just one-third of the way through the season?

In short, yes…sometimes. Let me explain.

By this point in the season, run differential in a vacuum can help you understand when a team’s been subject to under or over-performance based on their run scoring and run prevention. It is statistically significant.

But using it to project future performance is definitely subject to team context - let’s say Atlanta lost Jurickson Profar to suspension on Monday. That would make the predictive power of run differential less helpful going forward, as the roster context is different than when they actually put up that positive run differential.

The good news is that the team context helps Atlanta here. Jurickson Profar played only a few games with the team prior to his suspension. Still, he’ll return in a little over a month and join a newly activated Ronald Acuña Jr. Those two players did very little to impact Atlanta’s positive run differential in the first third of the season. But they’ll be able to help the rest of the way (or most of the rest of the way, in the case of Profar). The same applies for Spencer Strider - he’s made only two starts so far this season, but it’s likely that he makes another thirteen or so between now and the end of the season, starting tonight in Philadelphia.

What can we learn from Atlanta’s run differential so far?

I want to introduce a concept from the godfather of baseball sabermetrics, Bill James:

The Pythagorean Theory of Baseball.

In essence, this idea states that a team’s runs allowed against the runs scored is more predictive of a team’s future performance than other common projection systems. And if you think about it, that makes sense. If you’ve outscored your opponents overall on the year but have a losing record, you’re likely losing a lot of close games and that’s something that regresses to the mean over a large enough sample size.

For an example of this, look at the 2023 Miami Marlins, who were outscored by 57 runs on the season but made the playoffs thanks to an unsustainable 33-14 record in one-run games. The next year they were just 23-20 in one-run games and stumbled and sold their way to a 62-100 season.

Now, there are caveats here, also - extreme blowouts either way can skew a team’s run differential. This year’s Atlanta Braves seem not to be suffering from this, though. They’ve scored ten or more runs just twice on the year and allowed ten runs just twice on the season. Those games were 10-0 and 10-4 wins (Miami, 4/4; Boston 5/18) and 10-3 and 10-4 losses (Dodgers, 5/3; St Louis, 4/22).

The team’s Pythagorean Record is 27-25, based on 216 runs scored and 205 runs allowed, and projects out to a 84-78 record. It’s safe to assume that they’ve underperformed based on their run differential. Can we verify that?

Let’s look at Statcast’s Expected Statistics leaderboard.

Atlanta’s hitters are universally underperforming their inputs, missing seven points of batting average, 36 points of slugging, and 14 points of wOBA.

Those other teams that also have positive run differentials but losing records?

Cincinnati’s actually overperforming all of their expected statistics in those categories, but are also skewed by a +32 run differential in their 14 blowout games, where they’re currently 8-6. That’s sixteen runs per additional blowout win.

By contrast, the Braves are 5-5 in their blowouts, sitting at +6 in run differential.

The Red Sox are closer to Atlanta than Cincinnati, sitting at 9-6 in blowouts but at just +21, a seven-run margin per blowout. They’ve also underperformed their expected statistics.

Arizona? 4-6 in blowouts but outscored by only six runs and underperformed their expected statistics.

It’s clear to any impartial observer that while some big blowouts have helped the Reds, the other three teams should be better down the stretch than they have been through the first third of the schedule.

But let’s go deeper.

WHY is Atlanta underperforming their run differential?

In short, all of their one-run games.

Atlanta’s played 22 such games, going 9-13 in those contests and tied with the Pirates for the most in baseball.

(The Pirates are 10-12 in those games, including two one-run wins over Atlanta in the series between the two teams earlier this month.)

And really, it’s these one-run games that explain why the Braves are underperforming their Pythagorean expectation. If you win a game by five runs but then lose three one-run games, you finish that stretch with a +2 differential but a 1-3 record. And in essence, that’s what is happening to the Braves.

Too many of the Braves' games have been decided on the margins lately, where even a minor mistake- a hanging slider, a misread in the field - becomes costly. Look at last Sunday’s loss to the Padres for an example of that, with the Austin Riley defensive error prolonging an inning for Gavin Sheets’ homer and then Schwellenbach and Lee missing their spots in subsequent innings and giving up two more homers.

This is a closing theme of Moneyball, by the way. As General Manager Billy Beane explained, “My shit doesn't work in the playoffs. My job is to get us to the playoffs. What happens after that is fucking luck.”

The Braves need to get back to their offensive ways, blasting teams and winning handily. Because when you play every team close - nine of Atlanta’s ten losses in May, as well as six of their wins, are by two runs or less - random variance, bad bounces, or missed spots end up playing outsized roles in the outcome.