Matt Kemp: Same player as he was last year?

No player on the Dodgers has been the center of drama and controversy this season as much as Matt Kemp has. After hitting .297/.352/.490 in his first full season last year as the Dodgers' starting center fielder, many had high hopes that the 25 year old Kemp would increase his ascension into super stardom in 2010. This season, however, Kemp has been anything but stellar. Currently he is hitting .257/.314/.443 and has watched his wOBA drop by over 40 points. Fans, the media, coaches, and even manager Joe Torre have attributed Kemp's regression to everything from a lack of hustle, to "bone-headedness", to  even his new girlfriend Rihanna. Yet one factor in Kemp's hitting that has been largely ignored is his Batting Average on Balls Batted In Play (BABIP). As you may well know, BABIP is often used to determine how "lucky" or "unlucky" a hitter is. This year Kemp's BABIP is .308, much lower than last season's .341 and his career BABIP of .350. Clearly Kemp is having poor luck this year, but how much is it affecting his production compared to years prior?

One such idea I came up with is to use a "three-year average." What I like to do is to take the average BABIP of a player's previous 3 years and see what a player would hit in the current season if his BABIP were that average instead. This is very much similar (in fact it's how I got the idea) to how economists factor out prices when comparing "nominal" to "real" GDP. This is often used to factor out the volatility inflation can have on production in an economy. Similarly, I use a three-year average to factor out the volatility a player's BABIP has on run-production at any given time. The reason I use a three-year average instead of "base years" (as most economists do) is for the sake of simplicity. And the reason why I don't use a player's career BABIP is due to large and small sample and the failure to capture trends (as hitters do tend to have "some" control over BABIP). Lets use an example:

Currently Mark Teixeira is hitting a line of .256/.362/.495. These numbers are far below his career line of .287/.377/.540, leading many people to wonder whether or not he's "declining." Yet his 2010 BABIP is currently .262, lower than any of the three seasons prior, and much lower than his career BABIP of .304. To figure out Tex's three-year average I take his BABIP of 2007, 2008,  and 2009 (.339, .316, .302) and get a "real" BABIP of .319. Clearly this is well above his "nominal" BABIP of .262. Now how do we find the production Tex would have if his current production reflected his the "real" BABIP? First, I need to find out Tex's batting average. I take the number of at-bats (454) and subtract the number of HR (23) and SO (69) to figure out how many balls Tex has hit into play (342). I then multiply this number by his "real" BABIP to figure out how many "non-HR" hits Tex would have, and add this number to the amount of HR he has to get the total number of hits (136). I then take this number and divide by the total number of at-bats he has had to get his "real" batting average. To figure out his "real" OBP, I take the number of hits I've previously calculated and add his BB (69) and HBP (8) together and divide that number by the amount of PA (536) Tex has. To record  his "real" SLG is even more simpler. I assume that Tex's ISO (.239) would stay constant and simply add that number to his "real" batting average, which I had calculated before. Thus Tex's 2010 "real" batting line looks something like this:


This is what Teixeira's 2010 line would be if his BABIP were similar to that of the previous 3 years. This line is actually much better than his stated career line of .287/.377/.540, and is not too far off from his 2009 performance of .292/.383/.565. Therefore "luck" or lack thereof has had a lot to do with Mark Teixeira's performance in 2010.

Let's take another example. Currently Adrian Beltre is having one hell of a year for the Boston Red Sox. His 2010 "nominal" line of .328/.366/.568 is his highest since 2004, and is well above his career line of .274/.328/.461. However, Beltre's 2010 BABIP is a robust .344; well above his career BABIP of .294 and his three-year average of .290. So what's Beltre's real production line for 2010? Using the procedures described above we get this:


These numbers are still better than his career or 2009 numbers, but they suggest that luck has also had a lot to do with his recent production surge.

So going back to our old friend Matt Kemp; how much has his "luck" hurt him this season? Well Kemp's BABIP the previous three years have been (.396, .361, .345) giving him a three-year average of .367. Using the procedures before we get this as Kemp's "real" 2010 line:


This line suggests that Kemp's OPS is 19 points lower than 2009, indicating his performance has dropped off a little as his ISO has decreased a little while his SO have increased by over 21% from 2009. However, this line is still very much close to last year's numbers than his "nominal" line of .257/.314/.433, suggesting that Kemp really hasn't been as bad as his numbers would otherwise suggest. So perhaps Kemp's so-called "defenders" are right. Maybe Kemp isn't lazy or "bone-headed." Maybe he just needs to catch a break?


Since people might ask for it, I'm going to post some "real" triple slash lines for several Dodger hitters:

Andre Ethier .318 "real" BABIP .293/.358/.502

Casey Blake .318 "real" BABIP .257/.329/.407

Rafael Furcal .325 "real" BABIP .293/.358/.469

James Loney .321 "real" BABIP .283/.333/.413

Russell Martin .338 "real" BABIP .258/.355/.343

Manny Ramirez .338 "real" BABIP .305/.399/.504

Scott Podsednik .326 "real" BABIP .283/.325/.368

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