It being an off-day, I thought it would be interesting to talk about a general baseball point that I’ve been thinking about. That is using career totals to identify the skillishness of certain results, especially as it relates to balls in play for pitchers.
Let’s think about career averages. Let’s say that inducing popups is a skill, and we have two pitchers who have seasons with opposite results.
|Pitcher||Season 1||Season 2||Career Average|
Since Arms McGee knows how to make hitters pop the ball up, he only gives a little back from his excellent first season. Pitchy Pitcherson, however was only a little unlucky in his first season. But he achieves similar results in his second season.
Now, what would these results look like if inducing pop-ups is not a skill? Well, the results in the second season would have nothing whatsoever to do with the results of the first season. Think of it this way: if you draw a Queen from a deck of cards, the odds of you drawing a higher card on the second draw are pretty poor, aren’t they? In fact, your “average card value” is almost bound to decline after that. However, if you were cheating (i.e. you were skilled at drawing cards) your “average card value” might stay around the same level of your initial Queen.
Here’s our hypothetical pitchers when inducing pop-ups is not a skill.
|Pitcher||Season 1||Season 2||Career Average|
In our example, both pitchers go in opposite directions, but the important point is that in the second year, neither pitcher is any more likely to post the extreme results of their first year. Now look at what this does to the career averages. There’s a gap of 11 between the career averages when pop-ups are a skill, and a gap of only 5.5 when pop-ups are not a skill.
If you increase the number of pitchers, and the number of seasons, this result will only get stronger. Stats that show a strong season to season (or inning to inning) correlation will have a much tighter cluster of career averages amongst the players who’ve accumulated a decent number of games played.
This being Bay City Ball, I made a graph that compares the spread in ability with a few different ball in play outcomes. The average of each ability is set to zero, to make the comparison easier. That means that the more pitchers are clustered around zero, the less skillish the ability is. I got my data from Baseball Prospectus. I should note that for the pop-up data, Baseball Prospectus tracks all pop-ups, whereas my previous look at this used data for infield-flies. The data consists of the ball in play totals for each pitcher with over six hundred balls in play from 2001-2010.
The difference between the very best groundball pitchers is about twice as far from league average as the same difference between the best and worst at giving up line drives. Homeruns per flyball and pop-ups per flyball tend to be much more clustered around average. That doesn’t mean that those two abilities are completely luck based, though. There are just enough pitchers far from average to say that most pitchers don’t control their pop-ups per flyball or home runs per flyball. But I don’t it’s correct to say that all pitchers do.
Because I’m fascinated by pop-ups, I took a closer look at that data. With this data I produced a list of pitchers of whom I’m most certain have some sort of pop-ups skill. These pitchers have induced the greatest number of pop-ups over average over the last decade.
Yes, that’s right. Barry Zito is the pitcher that I’m most certain has pop-up ability. The average for all pitchers in the sample was about 21%. Zito has given up about 79 more pop-ups than the average pitcher would have with the same number of flyballs. What the rest of these pitchers mostly have in common is the tendency to keep the ball in the air, which makes sense. It’s probably a lot more fun to be a flyball pitcher when it leads to more weak contact for you.
The rest of the Giants starting staff is a little more unremarkable. Matt Cain is solidly above average at getting the pop-up (30 above average in his career). Tim Lincecum is about as below average at it -he’s missing 20 pop-ups over the course of his career. Sanchez and Bumgarner are look indistinguishable from average, with Bumgarner not really having been around long enough to definitively say.
Pop-up ability is rarer than the ability to get groundballs, or even avoid line drives. That doesn’t mean it’s non-existant.It does mean that you should give a pitcher a few seasons before you make any judgements about it, though.