Watching a team struggle in key games in September is possibly the most painful part of being a baseball fan. Sometimes they turn it around, but on some occasions a fan base watches a team go from a near certain playoff birth to watching October baseball. If it looks like your team might fall apart what is it that should worry you most? My guess is that it should be mental lapses, which would be the most likely thing to increase if the team is feeling pressure.
Mental lapses have a couple of possible proxies in baseball statistics, and one would be errors. Teams that are on the path to collapse might be identifiable if they start having more blunders in the field than they had earlier in the year. Historically it looks like this might be true. Coolstandings has a list of some of the greatest collapses from a playoff odds standpoint. Eight of the top ten collapses show an increase in errors during the month of September.
Only the 2011 Braves and the 1999 Reds had lower errors per game in September while collapsing and the Reds were pretty close to the same as the season as a whole. These gaps are also somewhat conservative since I included September in the whole season number, so the differences from the rest of season would be greater. Also, the September number includes regular season games that end up in October. As you an see, the difference on average for the collapsing teams is .117 more errors per game or 17.6% more errors per game than their season as a whole. The 2011 Braves might be the exception that proves the rule as they were way, way better in September at avoiding errors only having 5 the entire month. If you take them out the average difference shows almost 25% more errors for collapsing teams in September.
This could be something other than mental issues. It is possible that errors are higher in general in September due to things like expanded rosters, but of course contending teams aren’t going to be giving a lot of opportunities to unproven talent and shouldn’t be subject to that sort of thing. Errors don’t need to be the only proxy either, as I think making outs on the base paths or throwing to the wrong base/missing cutoff men sorts of mental lapses might work too. Maybe it work better to add up all “mental mistakes” and then look for differences. We could also look at it in a sort of contagion effect, but I am going to need a site to start giving monthly splits for all team data in an easily accessible way first.
Pressure and other intangible sorts of ideas are always hard to directly study, but we have all felt it manifest in our own lives so we can’t expect professional athletes to be immune to such things. Watching the Royals the last two weeks or so I have felt like this is happening at times (though Lorenzo Cain literally just smashed a three run bomb off of Chris Sale). Any Oakland fans feel like they have seen this too?