How long does a baseball season “need” to be?

The major-league baseball season is, far and away, the longest of any major team sport. It is twice as long as the NBA and NHL seasons; approaches five times as long as a MLS campaign; and is nearly ten times the length of an NFL season. The standard explanation is that this is necessary to even out all the randomness. It is true that, on any given day, the “better” team may not win a baseball contest. There’s enough randomness and chaos (in the mathematical sense) to make the outcome less determinable than the NFL. A fraction of an inch on the bat is the difference between Pavin Smith’s grand-slam on Monday, and a forgettable fly-ball to the outfield.

But the reality is that you typically do not need 162 games to determine who are the best teams, or who should qualify for the playoffs. Now, there are exceptions, of course. Who can forget the 2019 Nationals? They started 19-31, but not only made the post-season, they won the World Series. However, you can get a pretty good idea of who’s going to be the post-season by looking at the standings surprisingly early. Simple math backs this up. If you’re a team whose “true” winning percentage is .450 (a 73-win season), you only have a 13.1% chance of going 12-8 over a twenty-game spam. Even if you’re a .500 team, the odds are still only about one in four (25.2%).

You can see this if you look at the way things unfolded in the chase for the playoff spots last season. The 12 teams who ended up making the post-season, would all have been there, if the season had ended after 150 games. [Note, for simplicity, I’m using “games” as the standings after the D-backs’ 150th game, as different teams played 150 games on different days] The only difference between the standings then and at the end of the season, was the Mets losing the NL East to the Braves. But both teams still made the playoffs. There was some shuffling in the order of the wild-card teams, e.g. the Mariners overtook the Rays. But, again, both sides got into the post-season.

Going back in steps of ten (look, I have a life, contrary to certain rumors...), the same applies at 140 games. And 130 games. And 120 games. Put another way, in terms of determining post-season entrants, the entire last quarter of the season was irrelevant. You have to go back to 110 games to find any change at all, and even then it’s the Rays simply being in a tie with the Orioles for the final wild-card spot, both sides having the same record of 58-52. A further increment is needed, back to 100 games, before we find the Brewers taking the Cardinals’ wild-card spot in the National League, and the Twins replacing the Guardians on top of the AL Central.

Going back further, the changes don’t exactly come thick and fast. If we check in at the 80-game point - so, less than half of a full season - we still find nine of the twelve playoff spots occupied by teams who’d be in the post-season three months later, after another 82 games. But let’s cut to the chase. The chart below summarizes the situation every 10 games through the 2022 campaign, listing the six teams in the AL and NL who would have reached the playoffs if the season ended at each point. In the case of a tie, I’ve given the position to any eventual post-season team, but they are in italics. A white background means the team got into the playoffs; a black one means they ended up missing out.

I have to say, determining the situation after ten games (actually, eleven, since the D-backs had a double-header for games #10 and 11!) was a bit of a bear. Five American League teams had 6-5 records, including most of the AL East. But the above is as good as I think I could figure out. Less than two weeks into the season, and more often than not (7 of 12), the teams in playoff spots would still be there at the end of the year. Five of the teams basically never dropped out of a post-season place for the whole season. Eventual division winners the Dodgers and Cardinals were already leading their groups; the Yankees were tied; the Astros were half a game out.

Which is why I’m bullish on the 2023 D-backs, though they have only 20 games in the books. They’re leading their division, and history tells us teams that start off with a 11-9 record often go on to do pretty well. Specifically, in the wild-card era, 40% of them went on to make the playoffs - and for the great majority of that time, only four teams in each league did so, rather than the current six, making 40% likely conservative under the current system. Now, there is clearly a LOT of water to go under the bridge. As the Angels and Twins show, leading your division after twenty games, does not guarantee you’ll still be playing into October.

But Torey Lovullo’s mantra of “downhill baseball” applies just as much to the season as to individual games. It is a lot easier to stay on top of the division than to claw your way up there, and the D-backs have already shown that the Vegas pre-season line of 75.5 wins does seem ludicrously low. Here’s to that continuing.