Around this time every year, you’ll hear and read from people who think players should avoid participating in the Home Run Derby because it leads to second-half swoons. Chris Davis is a common example. In the first half of the 2013 season, he had a 1.109 OPS with 37 home runs in 95 games (an average of one homer per 2.6 games). He participated in the Derby, getting eliminated after the second round. In the second half of the season, he had a comparatively meager .854 OPS with 16 home runs in 65 games (an average of one homer per 4.1 games).
A tweet circulated on my timeline earlier today which compiled the triple-slash lines of all Derby contestants over the past three years, comparing their first-half numbers to their second-half numbers. As a group, the second-half numbers were noticeably lower.
Maybe there were two or three players whose mechanics suffered as a result of participating in glorified batting practice. Maybe Davis is even one of them. But Derby contestants are players putting up some of the best numbers among their peers in the first half. Simple mean regression is a much better explanation for the disparity in production. You could take, for example, All-Stars whose first names begin with a certain letter and compare their first- and second-half production. My money would be on the first-half numbers being much higher than those of the second half. And that’s just because they belong to a group of first-half overperformers: All-Stars.
Indeed, there were 18 Derby participants since 2000 whose first name has started with J. 11 of them saw their OPS decline in the second half, including six players by more than 140 points. Only two participants saw their second-half OPS rise by more than 80 points. This simply proves the old adage, correlation does not imply causation.
|Player||Year||1st Half||2nd Half||Diff|
The Derby-as-swing-ruiner hypothesis has been thoroughly debunked over the years, so I am not breaking new ground here. But it’s good to have a reminder that your favorite player’s second-half swoon is almost certainly due to good old fashioned mean regression and the Home Run Derby shouldn’t be made the scapegoat.