Matt Kemp’s 2010

Even after last night’s 2-for-6 performance against the Arizona Diamondbacks, which included an opposite field homer hit off Rodrigo Lopez, Matt Kemp is falling short of expectations. His defensive struggles have been well documented, but he’s also having a mild season at the plate. Prior to 2010, ZiPS projected Kemp to bat .300/.354/.501 and post a .374 wOBA. CHONE predicted a .305/.358/.501 line and a .376 wOBA. Instead, L.A.’s center fielder holds a .265/.324/.473 triple-slash, with a .337 wOBA. Why has Kemp’s lumber been lacking?

Despite the downturn in his slash stats, there are some positives to be found. Before the season began, I highlighted Kemp’s offensive maturation. Kemp gradually displayed better plate discipline, upping his walk rate each season from 2007-2009. That trend has continued, as he’s walking 8.2% of the time in 2010. The 25-year-old isn’t chasing pitches out of the zone near as much as he used to:

In addition to showing better patience, Kemp is hitting for plenty of power — his ISO is a career-best .208, and his 16.5% home run per fly ball rate is his highest mark since his first brief stint in the majors back in 2006.

So, Kemp’s secondary skills are better than ever. Why, then, is his line lethargic? He is punching out 28.4% of the time, his highest figure since ’06. Kemp’s not making as much contact on in-zone pitches this season — his Z-Contact rate is 77.8%. It’s true that Kemp’s in-zone contact rate has always been below the 88% big league average, but his 2010 rate comes in below even his 81.8% career average.

Also, Kemp’s BABIP is .321 this year. For reference, his career BABIP is .355, and CHONE (.359 pre-season BABIP projection) and ZiPS (.361) thought he’d post a BABIP around that mark. Kemp’s rate of hits on balls put in play has varied wildly over the course of his career, while his underlying skill set hasn’t changed much. Here are his BABIP figures from 2006-2010, compared to his expected BABIP totals. xBABIP is based on a hitter’s rate of home runs, K’s, stolen bases, line drives, fly balls, pop ups and ground balls.

Kemp’s actual BABIP is 13 points lower than his xBABIP this season. It’s worth noting again that the simple xBABIP tool linked to above uses stolen bases as a measure of a player’s speed. Speed has a positive correlation with BABIP. That could work against Kemp this season — after being an adept base thief in 2008 and 2009, his SB performance has been terrible so far.

The two previous seasons, Kemp was an asset to fantasy owners in the stolen base department. In 2008, Kemp swiped 35 bases and got caught stealing 11 times, a 76.1% success rate. He then stole 34 bases in 42 tries last year (81% success rate). In 2010, he has 10 steals and 10 CS apiece.

Baseball Prospectus’ base running stats tell the story. Here are Kemp’s Equivalent Stolen Base Run totals over the years, showing how many runs he has added on SB attempts compared to the average player. I also included his overall Equivalent Base Running Runs figure — in addition to SB tries, this all-encompassing number includes base running advances on ground and fly ball outs, hits and other advancements on things such as passed balls and wild pitches. Kemp has cost the Dodgers on steals this year, while faring quite well in the other facets of base running:

It’s highly unlikely that Kemp has suddenly become a lousy base stealer. But the SB downturn, coupled with his defensive issues, is peculiar.

Matt Kemp has frustrated plenty of people this season, but there are plenty of reasons to expect improvement during the second half. He’s abstaining from junk pitches thrown out of the zone and displaying excellent power. His BABIP will likely climb, too. If he can put the bat on the ball more often on in-zone pitches and start sealing bases like he did in ’08 and ’09, Kemp should resume being a fantasy stalwart.