Yes, Pennants Can Be Lost in April

When looking at most April stats, especially the basic ones, I spend a lot of time issuing disclaimers about small sample sizes. After all, any player can do just about anything in 25 or 50 or 100 plate appearances. I’m pretty confident that Joey Wiemer is not going to end the season as the NL MVP, and that Hunter Barco won’t finish the season with the worst WAR in major league history. But conversely, when we’re talking about standings, even if bad/good starts shouldn’t necessarily overconcern us about a player’s future, when it comes to teams, playoffs are determined by wins, which are cumulative numbers with razor-sharp margins. It’s not the end of the world if Cal Raleigh, because of his slow start, finishes with 38 homers instead of his projected 41 (ZiPS DC), but it may doom the Mariners if they underperform their projections by three wins.

The season is just a week old, but there are already sizable impacts in playoff probabilities around the league. To demonstrate this, I ran ZiPS overnight to get the updated playoff odds, so I could compare them to the preseason projections. Six teams have seen their playoff odds change by at least five percentage points. Here’s the full table, as things stand on Friday morning.

To put this into context, just after last year’s trade deadline, only four teams saw their ZiPS playoff probabilities move at least five percentage points. The number was eight teams in 2024, three in 2023, and six in 2022. In other words, a week of games is about as impactful as a trade deadline.

Expectations for teams, by and large, haven’t changed. Not a single team saw its rest-of-season roster strength change by more than .007 of winning percentage, or 1.1 wins per 162-game season. It’s just what is baked into the cake. Those wins and losses have already been accumulated, and even a being of divine providence would have trouble changing them at this point.

ZiPS has been running standings projections since 2005, so I have a couple decades of data to pull from. To get a more empirical, less projection-y look at how easy it is to lose a playoff spot in April, I took all 83 teams with a median outcome of 90 or more wins going into the season. I didn’t include 2020, for obvious reasons. Just to head off one particular vein of argument, yes, 83 teams is a good number fewer than the 161 teams that actually won at least 90 games during the seasons in question. But that’s as it should be. We don’t expect all 30 teams to hit exactly their 50th-percentile median projections in a given season, but for three teams on average to hit their 90th-percentile projection, six to hit their 80th, and so on. If your median projections don’t have less variance than the actual results, you’ve likely done something terribly wrong with your model!

Anyway, I took the 90-win projected teams and looked at their worst performances in April. A full 26 of those teams finished the month with a losing record. And for most of those teams, it wasn’t just getting one of their fated bad runs over and done with early, an idea I usually deride as “Baseball Calvinism.” From a preseason average projected win total of 92.5 wins, they had an average finish of 85.2 wins, with slightly less than a third of them (8 of 26) finishing with at least 90 wins.

Three of the 26 teams did manage to come back and beat their preseason win projection. Props to the 2006 Twins, who got off to a 9-15 start but still beat their preseason projection by nine wins.

What would the cost be of a bad April this year? To simulate bad Aprils, I ran the rest of this season 30 more times, each time making the team in question win four fewer games for the rest of April than projected, distributing the extra wins randomly in each simulation to the teams that it plays over the next four weeks. I then compared the change in each team’s playoff percentage, both to today’s projection and to its preseason playoff percentage. I’m also going to assume that the underperforming teams don’t actually see their team strength get any worse over those four weeks in order to isolate just how big a deal actual results are, with no change in expectation.

With a bad April, every team in baseball except for the Dodgers becomes just about a coin flip or worse to make the playoffs. For teams like the Yankees and Cubs, both considered likely to make the playoffs coming into the season, it’s a serious drop-off, but relatively a flesh wound, as they have plenty of “outs” remaining to draw. For teams like the Cardinals, Reds, or Twins, a bad April is essentially an evisceration, with a strong majority of their playoff scenarios disappearing into thin air.

What does this all mean? If you’re a playoff contender, and you underperform in April, you should consider your record very seriously, even if your opinion of your team’s quality is completely unchanged. That means that adding wins is necessary now; don’t take a wait-and-see-where-we-stand-two-weeks-before-the-deadline approach. It can be hard to add wins this early in the season, but teams with bad starts really should be considering trying to catch lightning in a bottle with their minor leaguers — not just with their top prospects, but also the guys who are tearing it up in Triple-A. And if the opportunity to make a big trade does arise, struggling teams should take it. April really is the cruelest month.