Adam Dunn’s 2nd Half Rebound

Adam Dunn as has had an unually huge drop in his production so far this year, especially in relation to his power. Over the rest of the season, people should expect some level of increase production because he really doesn’t that much further to drop. By looking back at players that had similar drops in power, the amount he should rebound can be estimated.

I wanted to look at how a hitter performed in the second half of the season and the next year after a huge power drop in the first half of the season. Thanks to our own Eric Seidman, I got a list of the players after 1973 that had at least 1200 PA in the 3 prior seasons, 100 PA before or on July 1st, 100 PA after July 1st and had a similar drop in production as Adam Dunn.

Over the previous 3 seasons (2008 to 2010) the 31 year old averaged an ISO of 0.271 and this season his ISO was 0.142, for a drop of 0.130. Using the above criteria for PA, I found 31 players that saw their 1st half ISO drop somewhere between 0.120 and 0.140. The following is the AVG, OBP, SLG and ISO for the 3 year average before the drop, the values for the 1st half drop, the 2nd half numbers and how the hitter performed the next year:

	AVG	OBP	SLG	ISO
3 Previous Year Average	0.291	0.373	0.527	0.236
1st Half	0.247	0.329	0.359	0.112
2nd Half	0.275	0.349	0.474	0.198
Year After	0.272	0.352	0.476	0.203

The performance of this group of players did jump quite a bit in the 2nd half of the season with the biggest increase coming in the form of power (SLG increases by 0.115 and ISO increasing by 0.086). Using these numbers to predict how the rest of the season would go, Adam Dunn would have a 2nd half triple slash line of 0.198/0.340/0.427.

One possible issue with the data, is that average age of the players in the sample is 33 when the drop occurred. This age is 2 years older than Adam is right now. To look at players closer to Adam’s age, I looked at the values for the players that were from the ages of 29 to 33. Fifteen players made the age cut (Mike Macfarlane,Tony Armas, Mike Schmidt, Jeromy Burnitz, Dale Murphy, Vinny Castilla, Reggie Sanders, Pedro Guerrero, Scott Rolen, Alan Trammell, Chipper Jones, Tony Clark, Gary Sheffield, Craig Wilson, Larry Sheets) and here are the results:

	AVG	OBP	SLG	ISO
3 Previous Year Average	0.283	0.369	0.526	0.242
1st Half	0.247	0.340	0.364	0.117
2nd Half	0.259	0.343	0.455	0.196
Year After	0.269	0.351	0.471	0.202

The only real difference I noticed was that this group did not increase their production as much in the second half, but their production in next year was almost the same as the larger group.

The above list of players is filled with players with various injuries and it could be a possibility that Adam was rushed back too soon from his early season appendectomy. Also, it has been voiced that some of the decrease in power has been to randomness, but I believe he is just not hitting the ball on average as far this season, for whatever reason.

From 2008 to 2010, he averaged hitting fly balls and home runs (using MLB batted ball data), 308 ft, 300 ft and 315 ft in each season. In 2011 he is averaging only hitting the ball 284 ft. Going to hittrackeronline.com, Adam has not hit a home run over 442 ft this season, while last season he hit 5 over that distance (479 ft being the longest). The drop in distance can be seen in his HR rate. Over his career Adam has averaged 22% HR/FB, while in 2011 it is half that value (11% HR/FB).

Adam Dunn drop off in power is fairly significant this season. Using similar players with such drop offs, it can be seen that he should rebound in the 2nd half and next season, but not close to what he was previously producing. The large drop in power can be attributed to him not being able to hit fly balls as far, thereby having less home runs. Adam Dunn’s future right not now does not look to be very bright.