Take Solace, Royals and Astros Fans, September Results are No Indicator of Playoff Performance

The Houston Astros have gone 11-16 since August 31st, squandering an 8-game lead over the Angels and a 4-game lead over the Rangers. A victory last night moved them a half-game back in front of the Angels for the final AL Wildcard spot, and 2.5 back of the Rangers as the final weekend approaches. The Kansas City Royals, meanwhile, have not had the pressure of holding on to a playoff spot, but have lost a large lead for the AL’s best record and have gone 11-17 since August 31st. The only AL team with a worse record over the last month than those two is the Oakland Athletics. The Angels, meanwhile, have been the best team in the AL over the last month, and have a chance to make the postseason that seemed a longshot, facing off against Texas in the final series.

History, though, does not say that is a particular disadvantage to come in cold once the actual postseason rolls around. (Houston, of course, has to hold on just to get there, as the playoffs basically start now).

I went back through the records of all the playoff teams after August 31st, going back to 1995, and then compared it to the postseason results. Here are the series win/loss records in the divisional and championship rounds based on winning percentage after August 31st to end of the regular season.

Of course, that includes series where the teams were virtually identical in their September records, so as not to have any meaningful difference between which one might be considered “hot”. What if we isolate it by the relative difference between the teams, by win percentage after August 31st? Here are the results of all series where one team had at least a .100 win percentage difference in September/October compared to the playoff opponent (for example, a team that won 65% of its games versus one that won 55%).

From the perspective of the “hotter” team, the series results were 31-30. If we move it to .150 or more, the “hot” team only won 13 of the 33 series. You’ll notice up above that of the teams that entered the postseason really floundering in September, with a win percentage of .424 or worse, they won 6 of 7 series before the World Series. That’s not an indicator that the Royals and Astros are destined for greatness, but it does go to show that limping into the postseason has not been an impediment once the playoffs begin.

[all data via baseball-reference.com]