Have Games Become Less Competitive Since the Trade Deadline?

The Astros bludgeoned the Mariners on Saturday in a game that was over by the time the fifth inning was complete, when Houston owned a 12–0 lead and win probability odds of 99.9% (the final score was 15–1). That game marked the 19th time in August that a team had won a game by at least 10 runs, the most in any month so far this season — and we still have a week left to go before September. Naturally, the non-contenders that sold at the trade deadline or sat still have different priorities at this stage of the season compared to the postseason hopefuls. But how much of an impact does the deadline have on the game’s competitive nature?

You could try to measure this with run differential. Prior to the trade deadline, the average margin of victory in a game was 3.54 runs; since then, it’s gone up to 3.75 runs. But the average increasing by a mere 0.2 runs per game is not a monumental change. Similarly, you could look at two teams that held deadline fire sales — the Cubs and Nationals — and look at their post-July 31 performance. Chicago is down three runs and the Nationals 1.2 in terms of run differential per game, almost entirely due to pitching and defense. But those are extreme examples, and aside from Max Scherzer and Craig Kimbrel, the impact talent that both dealt away was mostly on the position player side.

Rather than just rely on anecdotal evidence, let’s take a probabilistic look at these outcomes. To test whether or not there is statistical evidence for the trade deadline creating measurable disparity, we’ll form two sets of discrete probabilities: one based on games through July 30 (prior to the trade deadline) and one based on games afterwards. Any games with a resulting run differential of greater than or equal to 10 runs will be grouped together.

Given the small increase in average run differential between the two periods, it’s no surprise that any change in probabilities is pretty small. But focusing on the left and right boundaries, you can see the differences that we’re looking for. While one-run games are still the most common, they’re happening a bit less frequently than they were before the deadline. The incidence of games decided by at least 10 runs, meanwhile, has gone from 3.9% of games pre-deadline to 6.0% after it. (Interestingly, run differentials in between the extreme values are pretty mixed.)

To see if that’s significant, let’s run those pre-deadline probabilities on the 313 games played from July 31 through August 22 and see how it compares to the real results. Out of 1,000 simulations, I got 104 samples with a mean run differential of 3.74 runs; in other words, around 10% of the time, a game lined up with the average post-deadline run differential. Simulated games ending with a run differential of at least 10, meanwhile, happened 48 times, or just a percentage point shy of the actual observed figure. Our intuition, and the game results to a lesser degree, may nudge us toward believing the trade deadline had drastic implications on parity in baseball, but it’s not very clear that it has.

A lot of other things have an impact on run scoring and run differential over the course of a season, though. To pick one: As the season transitions from April and May to the summer months, scoring typically goes up, and run differentials increase along with that. This season has followed that convention somewhat, but these last few weeks have made August a notable exception where run-scoring has dipped from July numbers yet run differentials have increased.

The simulations from earlier did not take these nuances into account, so there may be an added argument that the deadline is having a bigger impact than the results of the simulation would lead us to believe.

Another way to look at this is analyzing performance after trade deadlines of past seasons. The last full season in 2019 yielded nearly identical average run differentials before (3.66) and after (3.64) the trade deadline. The bigger issue, however, is that each deadline has its own unique impact on the season, and 2019 was a bit of a dud in that regard, with only a handful of truly impactful moves.

I’m not saying the bevy of sellers at the trade deadline isn’t detracting from the competitiveness of some games for the rest of the season. The Orioles are currently in the midst of an 18-game losing streak, but let’s not forget, that’s their second double-digit losing streak this year, and Baltimore was more or less silent at the deadline, too. And while most of the beatdowns over the last few weeks have come at the expense of sellers and teams far outside of the playoff picture, the Rays, owners of the best record in the American League, lost 20–8 to the Red Sox and 12–0 to the Twins within a span of a few days. Blowouts can happen to anyone at any time.

I have my reservations, but there is certainly credence behind the idea that teams that traded proven major leaguers away are more at risk of losing by a lopsided margin than before. But even these teams tend to be more competitive than we give them credit for. On Monday, for example, the Royals (on pace to lose 89 games) beat the AL West-leading Astros on the road, and the Rangers (on place to lose 106) rallied late to force the wild card-chasing Red Sox into extra innings before ultimately taking the loss. We’ll probably have a few more blowouts in August, but that’s probably just as much a function of baseball being baseball as it is a growing talent discrepancy between teams.