If you keep up with various statistical analyses, or “sabermetrics”, if you will, you may have read a few things over the years that challenge some of the conventional wisdom often heard coming out of various baseball media.
Firstly, there’s the myth of team momentum. For every 2011 Cardinals team that makes an incredible run to end the regular season and parlays that into postseason success, there’s some other team, now lost among baseball’s vast history, that got hot in September and made a quick exit in the playoffs. Problem is, people tend to remember the times when the former occurs, and conveniently forget the latter. A little thing called “confirmation bias”.
I apologize for my lack of a link on this particular topic (though please direct your attention to the right for an interesting result), but the fact is, winning down the stretch has very little to do with how a team will perform in the playoffs, for better or worse.
Secondly, there’s the myth of individual momentum. The idea that because a player is in a slump, he will continue to be in a slump. This one almost seems silly when you say it out loud (of course players don’t stay in slumps forever), but it’s still fascinating how often we all fall into the trap.
To put on my nerd glasses for a moment, this concept often comes up in fantasy sports. As in, let’s take a look at Player X’s performance over the last two weeks to determine if we should start him this week. It’s similar to the small sample size pitfall. If you’re not going to trust your player because he’s struggled recently, then why is he on your team. Logic tells us that he could turn at any moment.
(Note: this holds true assuming all other factors remain constant. This doesn’t take into account things like a player getting fatigued as the season goes on. In that case, there could be a legitimate reason for a decrease in performance that may linger.)
This is all to say that none of those things influenced me to look at what I’m about to show you. In many ways, I merely view this as interesting information. Possibly, it could be an analysis of consistency, but I don’t know that it necessarily indicates what we might expect from future performance. Below is a five-start moving average for starter ERA for the Reds’ five starters this year:
I purposely left the labels off. Can you tell who’s who?
There’s lots of interesting observations to make. You might suggest that green has been the most consistent starter. Light blue might be the “weak link” of the group (if only slightly), and darker blue could potentially be the ace, though red isn’t far behind. Purple, which seems to have severe ups and downs, has turned it on lately and may be the most dominant guy on the staff right now.
There is certainly more to glean from this picture. What I really started wondering is who would you most trust in a postseason game right now. Earlier I discounted the idea of making a decision based on a player’s current hot or cold streak, but would you feel the most confident trotting out Homer Bailey right now, considering he has a 1.66 ERA and 5.5 K/BB ratio in his last three starts? Or Bronson Arroyo, who hasn’t given up more than 3 ER in a start since early August?
I ask the questions, but at the end of the day, I think it’s obvious that you stick with your aces. The other thing to consider is that five starts is somewhat arbitrary, and more prone to bigger swings than, say, a ten start trend. For instance, over his last ten starts Latos has a 2.67 ERA, but because he gave up seven runs four starts ago (an anomaly for him of late), his five start average isn’t great.
Speaking of swings, it might be a good idea to check out FIP trends here as well, since ERA can be, you know, misleading at times (there’s that saber-talk again):
To be honest, this probably should have been what I looked at the first time, but it actually provides a fairly interesting comparison to the ERA graph. It’s much more stable, for one. For another, it may be a more accurate reflection of performance. Many of the same trends emerge, however. Bailey’s recent performance is even more striking. Conversely, Leake’s more troubling. Arroyo appears just as consistent. Latos’s early season struggles are quite noticeable. And Cueto’s “struggles” of late are a bit subdued.
In the end, as we near October baseball, it’s interesting to take a retrospective look at the guys who will be leading us into battle.
Follow Aaron on Twitter @aaronjlehr