The Home Run Derby and Its ‘Carry Over’ Effect

Help us all if one of the home run derby contestants goes on a cold streak. Someone, somewhere, will mention that the slump started right after the player partook in a contest all about hitting the long ball, and naturally hasn’t adjusted his mechanics or mindset since. The poster boy for the post-derby slump is Bobby Abreu. He hit a of homers in the first half, only a few in the second, yet still wound up with around what you would expect from a slugger on the wrong side of 30.

Any fears of a powerless second half because of the derby are extinguished when you examine the last three seasons of participants. Taking all 24 of their first and second half homerun and plate appearances, I found that the difference is marginal, and can probably be attributed to regression more so than anything derby related.

First half HR/PA%: 5.52
Second half HR/PA%: 4.79

Over the average second half (377 plate appearances) the difference is 3 home runs. You could blame this on a meaningless competition, or you could chock it up to regression. Why are these guys even chosen for the event? Because A) they’ve hit a ton of homers in the first half or B) they’ve hit a ton of homers in the past. “A” is the key to the regression pie. Let’s take a look at the biggest drops.

Justin Morneau (2007) 6.6% /2.3%
Dan Uggla (2008) 6.6%/3.3%
Chase Utley (2008) 6%/2.8%
David Wright (2006) 5.2%/2.2%
Lance Berkman (2008) 5.5%/2.6%

Each of these guys outdoing their previous numbers and the league’s numbers; a combination which signals some regression is on the way. That means, it’s not a physical or mental adjustment some players are going through, but rather a statistical one.