Playoff teams and records

There are two things wrong with this post. One, it’s way too early to say anything about the playoffs. Two, all publishing conventions scream not to publish posts on Saturdays. But after seeing one too many people saying something akin to the following:

I decided I had to act fast, so here we are. Let’s get this over with.

Out of the 156 teams to have made the playoffs since 1995, when Major League Baseball first introduced the wild card, 60 of them had a losing record against teams that had a winning percentage above .530 during the regular season.

Let me repeat that in a slightly different way: 38.5% of playoff teams in the last 19 years had a record below .500 against playoff-caliber opponents that season.

All of you should be giving a collective “no duh” right now. This is a fundamental aspect of baseball, one team wins and one team loses and when you include a couple extra good teams who just missed the playoffs, you invariably have some teams with an above .500 record and some with a below .500 record against playoff-caliber opponents.

And yet most people if asked blindly would probably say a below .500 record against playoff-caliber opponents was a near death stroke to playoff hopes. Just four games into the series against the Braves and some have pegged the Nats 1-3 record as a key indicator that they’ll miss the playoffs in 2014.

Yes 38.5% does not mean the odds are in a team’s favor if they finish below .500 against playoff-caliber teams, nor is that a complete list of every team that does so. Still, that’s a hefty percentage of teams.

“But Jamessss,” you say incredibly whiny in my imagination. “Just because they make the playoffs doesn’t mean they’ll do well. Surely being below .500 against playoff-caliber teams means they won’t succeed in the playoffs.”

To which I answer “Shut up, of course I have some data on that too and stop calling me Shirley.”

Here we see the aforementioned 156 playoff teams with the number of wins they had in the playoffs compared to their win percentage against playoff-caliber teams that year.


Well that’s just a gigantic mess that has no correlation whatsoever. But that isn’t very rigorous and you dear reader clearly demand more. So we press on and calculate the Root Mean Square Error (RMSE) using the formula for the best-fit line displayed on the graph above. This will tell us how accurate our predicted playoff win total based on the win percentage is compared to the teams’ actual playoff win total. For this data the RMSE is equal to 3.7 wins. In other words, on average our prediction is within 3.7 wins of the actual total in either direction.

To better illustrate this I grouped teams into buckets by their win percentage against playoff-caliber opponents, with each bucket covering .050 points of win percentage. Here’s a graph of each bucket’s average number of playoff wins compared to their average win percentage against playoff-caliber teams.


Here we now see a much nicer linear relationship, with a good correlation coefficient. The formula for this best fit line has a RMSE of 3.8 wins, essentially in line with our previous estimation.

So now we have a question to ponder: how helpful is being able to predict on average a playoff team’s total playoff wins in a season within 3.7 wins? That’s practically an entire series and is in fact more wins than a team needs to win the divisional series.

So we can see there is a bit of a correlation between these two factors, but not enough of one to be particularly helpful or worried about. And especially not in April when we don’t even know which teams will end up winning 86+ games by the end of the year. So if you would like to freak out over every little occurrence in every single game, please do so offline. Or maybe talk to your doctor about some anti-anxiety medication.


  1. Based on a tweet guiding me here to say it addresses my point, I’ll bite and post a comment. Either I’m not conveying my point very well or it’s being completely misconstrued (or maybe a bit of both). 140 characters can occasionally make it difficult to get a point across.

    Yes… The Nats should be expected to lose more often when playing the better teams in the league than they should against lesser competition. As you mentioned above, “no duh.” That said, there’s a pretty significant difference between under .500 (the figure you use) and the .311 winning percentage (14-31) that the Nats actually had against those NL playoff teams last season. Just a .400 record (18-27… again, not .500) in those games in 2013 would have put them in a play-in game against Cincinnati to go to the wildcard game. Just three MLB teams last season (Astros [.315], Marlins [.383], White Sox [.389]) finished with a sub-.400 record on the year… so yeah, there’s a pretty wide gap between .400 and .500.

    Baseball’s a funny game. Sometimes the ball bounces the right way for a couple of weeks in a row. Sometimes it bounces the wrong way for nearly a month. A 162 game schedule allows for quite a bit of random variation and chance to rear it’s ugly head every now and again. There’s a chance that all it will take is the occasional lucky bounce or a bloop hit (last night’s game, anyone?) that falls the right way instead of the wrong way. Perhaps some have said “can’t” or “won’t” or “choke.” I never have, nor will I. I’ve simply said that they need to play better against those teams. I’ll continue to do so. There’s no doom or gloom in that.

    In all honesty, it should be difficult for them to repeat the same woes that they had last season against other contenders. They were outscored 181-125 in those 45 games. This leads us to a Pythagorean W-L Percentage of .323. While .323 obviously still isn’t good, it’s better than their actual win percentage was against those teams. In other words, run differential says they were better against those teams than their record indicated (there’s a case to be made that they were unlucky). Either way, their .311 winning percentage in that (cherry picked, yes) 45 game slate against other contenders was worse than the 51-111 Astros overall winning percentage (.315) last season. Again, it should be difficult for the Nats NOT to improve on that performance.

    The cutoff to make the playoffs last season was 90 wins. While there’s clearly not enough data to go on based on 10 games in the 2014 season, we should probably expect the cutoff to be somewhere around there again (88-90 wins). Playing ANY 45 game slate at that .311 level means that a team is going to have to go 76-31 (.710) in their other 107 games to reach that 90 win plateau. How hard is it to play .710 ball? In the past 50 years, only the 2001 Mariners have performed that well over a full season. Only six MLB teams in history have performed that well over a full season. So yeah… They’ll have to play better against their fellow contenders than they did last season (again, different from saying that they “can’t” or “won’t” play better against them)……. or play like the 1927 Yankees (.714) against everyone else.

    Here…. Let’s make it short, sweet, and positive (still can’t fit this in 140 characters).

    The Nats performance vs. 2013 playoff teams creates an opportunity for them in 2014. It should be difficult for them not to improve on last season’s .311 Win% against them, so it’s a clear area where they can gain ground.

    Four games against the Braves haven’t changed that.


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