Why do we believe that David Ortiz’s unimaginably bad April and May should nearly be ignored when projecting his performance for the rest of the year? Why should we believe he has the skills of a .259 / .352 / .566 hitter (his numbers from June 6 to August 24) rather then those of a .227 / .320 / .439 hitter (his overall season numbers)? Isn’t this “cherry-picking” of the worst sort? Why would you toss out a significant chunk of a season like that?
It’s not a trivial question: if Ortiz really is a 759 OPS hitter now, he should be getting no PT for the Red Sox, not when Casey Kotchman is sitting on the bench. In fact, some on SonsofSamHorn.net (from which much of this post is adapted) have been arguing just that: bench Papi, he’s toast. But if he’s actually a 918 OPS hitter, that would be crazy.
The first thing to understand is that you could play Stratomatic Baseball or Diamond Mind from now until the day you die and not see a .439 slugger put up a .288 SA in his first 221 PA and a .566 SA in his next 264. Ortiz’s HR / Contact has gone from .007 to .106; the odds against seeing that in a random simulation are something like 3,823 to 1 (chi-square, p < .0003). [NB: Yes, I know that chi-square is not exactly accurate with any of the n < 5, but it’s close enough for sabermetrics.]
It’s important to understand that streakiness is real. Player seasons which divide like this and give ridiculous odds of happening randomly according to chi-square are commonplace. That serial day-to-day correlation is not significant does not disprove the notion of streakiness; it just fails to give positive evidence. Remember that a correlation does not measure the strength of a relationship; it measures the strength of a relationship minus the noise. Add sufficient noise, and any real relationship can fail to show a significant correlation.
The second thing that’s crucial is that we have a very good explanation for why Ortiz (or any hitter and especially any aging hitter) could have such a miserable stretch of season. When looking at big splits, “do I understand how this happened?” is one of the two crucial interpretive questions you must ask yourself. (The other—and sometime it’s the same question—is “did I look for this split to confirm an existing hypothesis or suspicion, or did I stumble on it while examining all of his splits?”)
The explanation (and here we shift from sabermetric mode to scouting mode, and it’s something that every sabermetrician needs to be able to do) begins with the psychological contrast between the “Big Papi” of legend and the Ortiz of April and May. From the ’04 post-season to the end of ’06 Ortiz may have been the most confident athlete you’ll ever have the pleasure to watch. I’ve done studies which showed that his success in walk-off situations literally had millions-to-one (maybe billions-to-one) improbability. He not only knew he could hit, he knew they couldn’t get him out when it really counted.
This absolute confidence disappeared when he started suffering the health problems that come with ordinary aging. In ’07 and ’08 his clutch differential was actually negative, which was just being average plus bad luck.
Compare the guy who knew that no pitcher in the planet could get him out when the game was on the line to the guy who told the press “Papi sucks.” Ortiz suffered a complete collapse of confidence, complete self-doubt.
Now, the way this affects hitting is that it causes you to think about mechanics while you’re up there. That’s the last thing you want to do; it’s got to be what people call “muscle memory.” I suspect former Sox #1 prospect Lars Anderson has struggled this year in part because he’s so damn smart, and I suspect that the success of guys like Wade Boggs and Manny Ramirez is directly correlated to, shall we say, their unlikelihood of ever joining Mensa. I think it took Dwight Evans half his career to stop thinking too much while he was up there. (NB: I’m not talking about the “what’s he going to throw me next” thoughts between pitches, just whether the hitter can shut out conscious thoughts about swing mechanics.)
It’s important to note that there were a few weeks where we had persistent reports that Ortiz was having great BP but was still struggling in games. BP gives you a chance to work on mechanics and, having made an adjustment, get it out of your conscious mind, let it settle into muscle memory, and take a bunch of repetitions. Bringing that to games can be a big challenge. It’s the reason why slumps last as long as they do despite hitting coaches, video study, and extensive extra BP. It’s absolutely like the “don’t think about elephants” dilemma. It’s not just that you have to get past the stage where you’re actively thinking about mechanics, you have to get past the stage where you’re thinking that you shouldn’t think about your mechanics. That takes repetitions and confidence. You have to literally forget you’re slumping. You can’t be trying really hard to relax.
To sum up:
Age and declining health – > increased likelihood of mechanics getting out of whack, at the purely physical level. Your knees hurt, you lessen the depth of your crouch, suddenly the swing is just a bit off.
Declining health -> loss of general confidence. You know you’re not physically the player you used to be.
Loss of confidence -> increased likelihood of thinking about swing mechanics while at the plate. Once the thought even crosses your mind that the swing might not be right, thinking about the swing while up there just makes things worse.
That’s how slumps start. And then the bad performance of the slump creates a further loss of self-confidence which leads to more thinking which leads to yet worse performance.
The reason why we can ascribe Ortiz’s epic slump to these psychological processes (writ much larger than usual) rather than to a fundamental loss of skills is obvious and trivial: his performance after the slump is over. The numbers are arguably even more dramatic than the ones I noted at the beginning, because in the 11 games after the PED story broke, Ortiz hit .114 / .204 / .136 in 49 PA, and according to his own testimony he wasn’t sleeping at night. Those 49 PA can actually be excluded by the same logic, leaving us with a “true maximum skill level” of something like .293 / .386 / .668, which is basically his season projections with a big power boost.
The reason why you don’t project him to hit like that the rest of the year is equally obvious and trivial: he is not immune to further slumps. There is even a small probability that the next slump will be extended, like the first one, but that is mitigated by two factors: he is much more likely to fear that he has lost his skills when he’s slumping at the start of the season rather than in the middle, and the April and May slump was exacerbated by the pressure of not having hit his first home run of the year (from the date of his first homer on May 20 to the end of the slump on June 5, he showed real signs of life, with a huge increase in pulled line drive percentage. This was precisely the period where he was reported to be having great BP.)
In terms of pure, peak, hitting skills, David Ortiz is probably 90% the hitter he used to be a few years ago. He probably has something like a 500% higher probability of getting himself into a serious sustained slump, especially at the start of the season (April ’08 was also terrible). The specter of these extended slumps diminishes his overall value, but they do not much affect our sense of what he’s likely to do in the short run.