July 16, 2010
Ahead in the Count
Why You Can Go for the Gold Ball and the Silver Trophy
Home Run Derbies have been around in some form for many years, but it officially became part of the All-Star Game festivities in 1985. Since then, hitters have frequently blamed the Derby for messing up their swings. Perhaps among the most notable is Bobby Abreu, who broke the record for the most home runs in the first round with 24 in 2005 at Comerica Park, but then struggled in the second half of the season with just six home runs after mashing 18 in the first half. Of course, this reeks of selection bias as Abreu tied his career-high for first-half home runs in 2005. Most hitters in the Home Run Derby are bound to be playing above their true talent level, and their subsequent regression to the mean in the second half is to be expected. Instead, many have been victimized by their own confirmation biases, correctly noticing declines that were due to come whether the hitters participated in the Derby or not.
Researchers have not found any evidence of an effect of “messing up a swing” by participating in the Home Run Derby. Before joining Baseball Prospectus, Eric Seidman tested whether the Home Run Derby hurt hitters in the second half of the season at the no longer available StatSpeak blog where several of us got our feet wet, and Eric found no effect on second-half performance. More recently, Derek Carty also found no effect of the Home Run Derby on hitters’ home run rates. Both of these writers compared the second-half performance of participants against their projections to control for selection bias.
However, it seems somewhat unlikely that a hitter could mess up his swing for another 2 ½ months by taking a few dozen swings for the fences. If there were any effect, chances are that it would be short-lived, so I decided to focus only on the 14 days before and after the All-Star Game to see if we could find a discernable difference. I looked only at participants of the 2004-09 Home Run Derbies, which included 48 hitters who had 2,592 plate appearances in the two weeks before the All-Star Game and 2,772 PA in the following two weeks. This would likely remove the selection bias, since a couple weeks right before the break are unlikely to affect whether an individual is asked to participate in the Derby (especially because the participants are selected about a week before the All-Star Game). However, it gives me a large enough sample size that I can at least look at totals and make inferences. It also removes the bias that there are more home runs per at bat in the second half of the season, primarily due to higher temperatures—early-July weather is pretty similar to late-July weather, so run scoring is similar before and after.
Hitters actually improved in the following two weeks as summarized for all 48 participants in my sample.
Hitters actually appear to be hitting for more power, with a weakly significant increase in extra-base hits per at bat (t = 1.44). However, there was also a weakly significant increase in strikeouts per at bat (t = 1.56).
However, there is a difference in between participating in the Home Run Derby and making a real run at winning it. Hitters who are eliminated after the first round may be unlikely to “mess up their swings” as badly as hitters who last two or three rounds. Below, I summarize the results looking only at hitters who made it past the initial round and who made it to the final round.
The sample sizes are getting somewhat small here to find statistical significance, but hitters who advanced to the second round did show a significant decrease in walks (t = 1.90) and a weakly significant increase in strikeouts (t = 1.30), which may suggest that the participants are struggling with their strike-zone judgment. However, they are clearly performing better overall.
So far, we can see that hitters do not seem to be showing any evidence at all that they mess up their swings by participating in the Home Run Derby. But what does it actually mean to say that hitters are messing up their swings? How often have you ever seen a major league hitter take a wooden bat and hit a ball over a fence hundreds of feet away and remarked to your neighbor, “What a terrible swing!” Home runs are typically hit on good swings! These hitters are not training themselves to ground out to the pitcher. They are training themselves to lift and drive a baseball a long way.
After realizing this, I thought it was only obvious that batted ball statistics might be the best way to look for effects on a hitter’s swing. Are they upper-cutting more? The answer is perhaps not surprising.
Suddenly, the effect of the Home Run Derby on hitters’ swings is becoming more obvious. Attempting to lift the ball in the Home Run Derby is causing hitters to carry that lift into their post-All Star Break swings. Hitters show a weakly significant increase in combined outfield and infield flies, which primarily are coming from their ground ball total. Of course, they appear to be doing rather well with these fly balls, hitting more home runs and for more power overall as seen in the tables above. Of course, this effect is only short lasting as the overall first half rate of combined outfield and infield flies decreases from 41.0 to 40.1 percent.
The set of hitters who performed relatively well in the Home Run Derby experience a similar effect to large group, although they appear to be hitting fewer line drives. This is especially true for those who advanced to the final round, as their line drive rates did go down by 5 percent in the two weeks after the break (t=1.95). However, it is important to remember that the additional fly balls were hit hard enough to actually show a significant improvement in their batting average and slugging average (12 and 48 points, respectively), indicating that although these hitters may be altering their swings, they are not harming themselves.
Hitters have become increasingly fearful of the Home Run Derby in recent years, but the changes that do appear to be occurring are probably helpful. There are worse things to do to one’s swing than to fine tune it to hit the stuffing out of the gold ball. In the past five years, more than $1.5 million has been donated to The Boys and Girls Clubs of America and Easter Seals by Major League Baseball, Century 21, and State Farm, thanks to hitters hitting gold balls, those when the hitter is down to his last out of each round, out of the park. On top of that, these hitters are training themselves to hit the ball harder, if also at a higher incline. This is a win-win situation, and an exciting (if not a little bit commercialized) event for fans. Next time you hear a player say that they are opting out of the Home Run Derby to avoid altering their swing, you will know that while those alterations might be real, they would also probably have been productive.