We fans like to think we know a lot about baseball. Maybe even more than the players and managers! Humans in general get emotional validation from thinking that we're very good at something, and for many of us that "something" is baseball knowledge. It doesn't even have to be statistical stuff -- any knowledge will do, because it makes us feel more invested in our hobby. It makes us feel like what we're doing is more worthwhile than it probably actually is. In some cases, we actually do know more than the players and managers: I, for instance, know how wOBA is calculated, the name of Kameron Loe's old pet boa constrictor, the expected run value of a sacrifice bunt, and the color of Michael Morse's car. I am not sure that Raul Ibanez knows any of those things.
So there are plenty of times when we get to feel like we know more about baseball than a manager or a player. But then... there are other times. For me, today was one of those other times. You see, as much as I've read about and discussed Dustin Ackley's lackluster 2012 offensive performance, it turns out that there's a very big and potentially rather important split that I missed completely. Dustin Ackley, on the other hand, knows all about it.
At lunch today I decided to check my Twitter feed, and the first thing that popped up was an article by Greg Johns. Dustin Ackley won't blame bum ankle for down '12, went the title. I clicked in and read it. Most local Mariners articles don't tell me a whole lot that I haven't already read elsewhere (mostly just because I read way too much about the Mariners), but this one has some quite interesting information, including Wedge's reveal that Ackley also had hamstring issues (kept quiet for "competitive reasons") and one rather gruesome detail about the relative sizes of Ackley's left and right calves (that can't be healthy).
One line in particular, though, caught my eye.
But Ackley gutted out the season, admitting only now that he had a hard time loosening up for day games in particular.
Huh. Day games in particular. That kinda makes sense, right? That with less time to warm up before the game, Ackley might have a harder time stretching out his injured ankle, and that might affect his performance? Thinking about it, I realized that all of the Ackley highlights I remember from last year came during night games. My curiosity piqued, I hit up Fangraphs for Day/Night splits to see if the statement had any numbers behind it. I thus discovered that Fangraphs doesn't carry Day/Night splits. Why would they? It's not a thing that you think of as having a big impact on a player's game.
Luckily, BaseballReference does carry such splits. I scrolled down Ackley's splits page to the Day and Night lines, and ... well, rather than describing my reaction to you, I will provide a representative GIF.
A good defensive second baseman with a .696 OPS was 2011 Omar Infante. He produced 2.7 fWAR, though he was penalized more heavily on offense than Ackley would have been due to playing in a more hitter-friendly park. A good defensive second baseman with a .460 OPS was 2012 Michael Martinez. You have never heard of Michael Martinez. Stop lying.
So. This is a thing.
This is a thing, however, that comes with several caveats. First (everybody with me now!): small sample size. 201 PA is not a whole hell of a lot, and it could have been a fluke. Just as we can't say that 2012 Road Seager is 2013 Real Seager, we can't say that Ackley's not-being-stretched-out was definitively having an effect on his day game performance. For what it's worth, this split did not exist in 2011, though Ackley says it wasn't until the end of 2012 that the ankle really started to flare up, and though 2011 is an even tinier sample size. Second: day games are often getaway games, and players often suffer during getaway games for fairly obvious reasons. Third, the stolen base splits that you'd expect to be there aren't. Fourth, Ackley could be getting confirmation bias, noticing that his stats in day games aren't very good and chalking it up to improper pregame work.
(You may, at this point, be wondering why I am failing to address the obvious point: that the split is predicated entirely on BABIP and home runs, and that his BB and K rates are constant. If you think about it a little more, I think you'll agree that actually supports the idea that the split is real. Of course his BB and K rates would be unaffected; Ackley's ankle doesn't affect his eye. If Ackley were really playing through an ankle injury you would expect worse quality of contact (lower BABIP) and less power (lower SLG) with the same BB and K rates, which is exactly what we see here.)
So yeah, there are problems with this evidence. But just because evidence has problems doesn't mean that it should be wholly ignored, at least in the world of baseball. We don't scrap WAR because it relies on often faulty defensive numbers. We don't ignore pitch framing data because it's not yet fully understood. The fact that reliever sample sizes are usually too small to really determine whether or not a reliever has a home run problem doesn't mean that relievers with home run problems don't exist.
This split would probably never be allowed into a court of law, or a peer-reviewed journal. But to be honest, there's almost no baseball analysis that would. We fans, even those of us with a statistical bent, are like shitty scientists. We can observe and hypothesize, but we can never test, so "what we know" is often really more like "what we think", and "what we think" is often based on correlation rather than proven causation. Jeff did an excellent job of addressing this point in his post about Jered Weaver's favorite rockpile. There, too, is a small-sample split backed up by quotes from players (or, more accurately, quotes from players backed up by a small sample split).
This day/night gap of Ackley's... it could be a real effect of his injury, or it could be a mirage. On the one hand, Dustin Ackley seems to believe it's real, and what numbers exist back it up in a big way. On the other hand, those numbers could very easily be faulty, and Dustin Ackley likes country music.
So I guess it's up to you what you want to believe. (Isn't it always?) I personally think that this was a real thing, that Ackley's day game performance was impeded by his ankle injury and that he should improve in day games in 2013. But then, I'm biased. I'm ridiculously optimistic about the Mariners, because I want them to do well, because that would give me emotional validation and make all this baseball-watching and baseball-reading and baseball-writing feel worthwhile. Your bias may vary. Maybe you would get emotional validation from the Mariners losing! Maybe you are a masochist!
Let's have a poll to find out.