Surprise! Kelly Johnson has gotten better this year

Recently, there was a note at the ever-excellent MLB Trade Rumors which said that the Atlanta Braves were likely looking to shop second baseman Kelly Johnson in the off-season.  The post noted that Johnson’s offensive production had declined this year, and the Braves do have fashion designer Martin Prado ready to play second next year.  I don’t mind the thought that the Braves might think Prado the better option.  He strikes out much less than does Johnson, although Prado seems to have a bit less power.  The part that I object to is the thought that Kelly Johnson is actually “losing it” this year.
Certainly, Kelly Johnson’s performance has suffered.  Last year, his slash line of .276/.375/.457 was rather nice for a second sacker.  This year, Johnson has slipped a little with a slash line around .260/.335/.400.  Not bad, but not what Braves fans were hoping for.  So Johnson must be losing his mojo, right?  Not necessarily.  In fact, I’d say that Johnson has actually gotten better this year.  How does a player drop 80-90 points worth of OPS and become better?  Read on.
First, let’s look at Johnson’s swing and plate discipline profile.  What’s important to know is that things involving plate discipline and swinging are the least given to variation over time.  It makes sense, because players are the ones who decide whether or not to swing the bat.  Hitting a home run requires cooperation of the pitcher, ball, and occasionally, wind.  This year, Johnson, a man with a strikeout problem, and a rather pedestrian contact percentage (around 80-81%, which is around the league median) actually started swinging more.  And that’s a good thing.  In 2007, on my twin measures of plate discipline, Johnson had a response bias rating of 0.84.  Now, response bias is a measure of how likely a player is to swing.  The ideal number is 1.00, because it minimizes the number of strikes that a player piles up, given whatever abilities he has on the other measure, sensitivity.  A number over 1.00 means that a player is swinging too much.  Under 1.00 means the player is swinging too little.  In 2007, Johnson’s problem is that he was taking too many pitches.  Johnson took a step toward fixing that.
My measure suggested that Johnson would benefit from swinging more, and he has done so.  Last year, Johnson swung at 39.3% of pitches.  This year, he’s been up around 45%.  (Maybe he reads StatSpeak?)  His strikeout rate has dropped (although only about a percentage point) in response.  Swinging more also drove down his walk total, but it meant that he was putting more balls into play.  So, let’s look there.
In general, a batter has pretty good control over what type of batted ball he puts into play.  The rates at which a batter hits grounders, flyballs,  line drives, or popups has pretty good reliability, so changes in them are generally not random in nature, but a change in either talent level or approach.  What happens to those batted balls is another matter.  More on that in a minute.  This year, Johnson’s LD/GB/FB profile went from 18.8%/42.7%/38.5% last year to something around 23%/38%/39%.  His flyballs are staying steady, but he’s turning some of his ground balls into line drives.  That’s good, because a line drive (which doesn’t leave the yard)  has about a 73% chance of going for a base hit, while a grounder has a 24% chance.  Line drives are good.
The fine folks over at FanGraphs are fond of using xBABIP for hitters.  Given a batter’s batted ball profile, we can get some sort of idea of what we might expect his BABIP to be (hence xBABIP).  The formula that FanGraphs uses is .15 * FB% + .24 * GB% + .73 * LD%.  Last year, Kelly Johnson’s xBABIP was around .290.  His actual BABIP was .330.  Johnson did 40 points better than expected given his batted ball profile.
The next question is whether that ability to “outhit” the expectation is something that is luck or skill.  As is my custom, I took four years worth of data (2004-2007) and calculated the xBABIP and the actual BABIP for all players, and found the difference between the two (whether they over- or under-performed).  It’s possible that some players just hit line drives or ground balls that are harder to catch than others.  If that’s the case, then we should see consistency over those four years in which players over-perform and which ones under-perform.  To test this, I used my favorite devide, the intra-class correlation (shot!).  The result was an ICC of .27 or .28, depending on how much I restricted the sample by the minimum number of PA required.
That means that there is a little bit of skill involved in over- or under-performing one’s xBABIP, although there’s a good deal more luck in there than one might expect.  Looking at it from an R-squared perspective, it’s more than 90% luck (or more properly, unexplained).  It’s not quite the level of non-correlation found in BABIP for pitchers, but it’s closer to that area than to the “three true outcome” neighborhood.  Perhaps it’s time for DIBS.
Going back to Johnson, it means that it’s likely that most of Johnson’s over-performance in the BABIP area was due to chance.  I haven’t run the numbers, but I’m guessing that expected BABIP is going to be a better predictor of future results than is actual BABIP.   Now, in 2007, Johnson’s expected BABIP was .290.  This year, it’s around .315 (more line drives!), which is what his actual performance has been.  All performance is talent plus luck.  So in reality, Johnson’s numbers from last year, which were fueled mostly by that high BABIP was mostly a matter of luck.  This year, he hasn’t had good or bad luck, but the underlying talent seems to have improved.  Atlanta’s management might be confusing luck with skill.
The one concerning piece about Johnson’s statline is the drop in HR/FB.  HR/FB is a statistic that is mostly in the batter’s control, and his drop from 10.3% to around 7% is a little concerning.  His flyball percentage hasn’t changed much from last year… they’re just not leaving the park as much, so perhaps there’s a power outage in there somewhere. 
With that said, Johnson isn’t exactly a world-beater.  Now that his luck has stablized, we’re getting a pretty good idea of what he’s really capable of.  According to VORP he’s in the bottom half of “regular” second basemen in all of baseball among such luminaries of Joe Inglett, Clint Barmes, and Mark Grooz, Grudsil, oh, you know who I’m talking about.  He strikes out way to much for a guy who doesn’t put up massive HR numbers.  My OPA! fielding system has him rated as a boring old average second baseman in the field.  So, while I can’t fault the Braves if they think they have a better option, I’d caution them to be a little more careful in how they make that decision.  Kelly Johnson is a symptom of a much bigger problem of the need to understand the separation between talent and performance.  He’s actually gotten better this year, despite what it looks like.

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One Response to Surprise! Kelly Johnson has gotten better this year

  1. [...] leads into the title of the post. Yesterday, Pizza Cutter, my colleague at Statistically Speaking, wrote an article about Kelly Johnson in which he discussed how performance is equal to talent and luck; last year, [...]

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