Victor Martinez’s early season statistics weren’t good. Most were pretty bad. He wasn’t getting on base, he wasn’t hitting for power, and because he plays a position that doesn’t utilize a glove, he wasn’t adding value on defense in the way Andy Dirks has done during his own offensive struggles.
But seemingly all of a sudden, Martinez is crushing the baseball. In the last 30 days, Martinez has a very respectable 112 wRC+ (what’s wRC+?). In the last 14 days he has a 170 wRC+. In the last 7 days, it’s 209. That is what the average person would describe as a trend, or perhaps a hot streak. Regardless of the cause or the sustainability of this performance, anyone can look at his numbers and recognize that Martinez’s performance is getting better.
I wrote earlier this year that Victor Martinez was having a particularly extreme case of terrible luck on hard hit balls. He was among the top handful of players in the game at making hard contact, but his batting average and power numbers didn’t reflect that. In fact, he was the only one near the top of the list who wasn’t hitting well above league average.
It made no logical sense that Martinez would make so much hard contact and not reap the rewards. It wasn’t really happening to any other hitter and it doesn’t really happen all that often in general. Hard contact is very highly correlated, and likely the cause of success in the batter’s box. But it wasn’t happening for Martinez?
The answer is actually so simple that it’s hard to grasp. Nothing was happening. Victor Martinez was doing nothing wrong. He wasn’t chasing bad pitches, he wasn’t hitting a dramatic number of popups or anything. Victor Martinez was the victim, if you can call it that, of something we statisticians call random variation.
Think of it this way. If a player’s true talent level is a .300 batting average, that means that over the course of the season, he’ll get 3 hits for every 10 at bats. But it doesn’t mean that he’ll get 3 hits in EVERY 10 at bats (that would mean performance uniformly distributed). Sometimes he’ll get 2, sometimes he’ll get 4. Sometimes he’ll get 8 and sometimes he’ll go 0 for 15.
Statistics are excellent and wonderful and we love to use them to measure things, but they have to be used properly. You have to understand what they mean. When Martinez was hitting .210, it meant to date he had gotten about 2 hits in every 10, but it didn’t mean that was his true talent level. He’s a .300 hitter in his career, this window was just a low point. A period of “bad luck” if you want to call it that.
Random variation means, in a simple sense and nontechnical sense, that the smaller a sample you look at the higher the likelihood is that you’re observing something that doesn’t reflect reality. Miguel Cabrera gets a hit around 33% of the time in his career, but if you look at any 3 at bats, you’re likely to see him have 0, 2, or 3 hits. That’s how sample size works.
This relates to Martinez because the underlying information about Martinez went unchanged during the slump. He wasn’t chasing pitches and he was making hard contact. The walk and strikeout rate looked fine. Good swings were turning into outs way more frequently than they usually do for him or for anyone.
And then all of a sudden it stopped. Somewhere in the last four to five weeks, Martinez just started getting those swings to turn into hits and he’s climbed all the way up to a .254/.311/.367 line after a .221/.290/.274 line in April. He’s not a different player, he’s just getting his hits to drop now and he wasn’t then. He’s taken two and half months of bad stats and is slowly erasing them.
His numbers were awful. Now they are amazing. Only two things can be responsible for that. One is a change in skill, health, or approach – none of which are evident. The other is a change in fortune – which appears likely. Victor Martinez is the poster child for a concept called “regression to the mean.”
Regression to the mean is an idea that suggests, in baseball, that when a player does something much better or worse than his previous career average it’s likely that he’s going to regress toward the previous average more often than he moves further into the extremes. You can think of regression to the mean as the correction in random variation over large samples.
In a small sample, anything can happen, but if you give something enough time, it will show its true colors. I’m boiling down a complex statistical concept, so well-versed statisticians shouldn’t analyze the wording too literally, but the amazing tear Martinez is on is essentially like the universe balancing out the really unlucky stretch he had.
It really is that simple. Take a look at his monthly performance:
It’s getting much better, sure. But there is something in the batted ball data I want you to see. This is a bit cluttered, but take a look.
He was hitting fewer groundballs than normal in April, and now he is hitting more to compensate. He was hitting fewer than normal line drives for the first three months, now his is hitting more. He was hitting way more flyballs that normal to start the year, now he’s hitting fewer. Everything is correcting itself. It’s not that he is now hitting like the career averages he set for himself, it’s that he’s now playing at the other extreme to balance out what happened before. The process for Martinez was good, but the results we all out of whack. Now the process is the same and the results are good.
This is a simple case of regression to the mean. There wasn’t anything wrong with Martinez that time couldn’t fix. The Tigers did just fine while he was “struggling” and now they’re getting the hot-hitting version of him as the race gets going.
In general, this should be a lesson to you that surface statistics can be deceiving. If you thought Martinez was a good hitter entering the season, you shouldn’t change your opinion so quickly when he has a low batting average for six or eight weeks. Almost always, unless a player is hurt (he never looked hurt), he will regress to the mean. He may not ever have the season he had in 2011, as that was likely his career year as a hitter, but he will look very much the player you expected. He’s been a 120 or so wRC+ hitter for most of his career and there is no reason not to expect something around 110 now that he is entering the downswing of his career.
Enjoy Victor’s hitting streak and power explosion now because you certainly earned it while he wasn’t getting hits. It’s often hard to take a step back and see the world with a wide angle lens, but it’s something we should do a lot more often.