Will Adrian Gonzalez Rebound?

Adrian Gonzalez was a disappointment last season. While his overall slash line of .299/.344/.463 isn’t terrible for most players, it represented a pretty big fall from the elite production he’s provided in the past. The culprit of his struggles wasn’t an injury, and, at age-31, Gonzalez is still young enough to stave off a major performance decline. Those factors have made Gonzalez one of the most difficult players to project this season. Unless he can return to form, Gonzalez’s days as an elite offensive first baseman may have already come to an end.

Gonzalez’s .349 wOBA was his worst offensive performance since he became a full-time starter. While a .349 wOBA isn’t all that terrible, it’s a far cry from Gonzalez’s peak years. From 2006 to 2011, Gonzalez averaged a .381 wOBA, putting him in great company. His .035 drop in wOBA last season was large, but not unprecedented. Since 1969, there have been 63 players who produced about the same wOBA as Gonzalez through their age-29 seasons. The following season, 30 of those players saw some decline in their offensive performance. Gonzalez’s struggles, however, were fairly extreme. Only nine players saw a bigger drop-off on offense during their age-30 seasons.

This actually might not be a bad thing. The following year, 16 of the players who saw their wOBA decline at age-30 managed to improve their offensive performance during their age-29 season. Remember, the sample in this case is 29 players since we have to exclude Gonzalez. The improvement wasn’t limited to guys who barely declined at age-30 either. In fact, of the 19 players who saw their wOBA decline by .020 points or higher, 12 of them made that up the next season.

All decline at age-30	Gain at age-31	.020+ decline	Gain at 31
30 players	0.007	17 players	0.020

The first column in the above chart shows the total numbers of players who saw their wOBA decline at age-30. At age-31, those players raised their wOBA, on average, .007 points higher. That’s a start, but it’s not enough to make people think about vintage Adrian Gonzalez. That changes a bit when looking at some of the drastic declines. The third chart shows that of those 30 players who declined, 17 lost at least .020 points of wOBA. The next year, these players saw a big boost, on average gaining .020 points of wOBA at age-31. That could indicate that the big drop-offs at age-30 are an aberration, and not a harbinger of further decline for Gonzalez. But can Gonzalez be expected to improve that much?

The two main areas where Gonzalez saw big decline was in his walk rate and his ISO. Compared to the players used in the first sample, Gonzalez’s drop was extreme.

Name	Age-24-29 BB	Age-30	Dif	age-24-29 ISO	Age-30	Dif	Age-31 BB	Dif	Age-31 ISO	Dif
Eric Davis	13.10%	11.70%	-0.014	0.239	0.094	-0.145	10.80%	-0.009	0.177	0.083
Kevin Mitchell	10.20%	8.70%	-0.015	0.243	0.142	-0.101	7.10%	-0.016	0.260	0.118
Bobby Bonds	11.30%	9.60%	-0.017	0.213	0.122	-0.091	10.90%	0.013	0.257	0.135
Don Mattingly	7.20%	7.10%	-0.001	0.191	0.106	-0.085	5.70%	-0.014	0.128	0.022
Jack Cust	18.90%	15.20%	-0.037	0.247	0.177	-0.07	16.00%	0.008	0.166	-0.011
Ryan Ludwick	8.80%	7.60%	-0.012	0.249	0.181	-0.068	8.70%	0.011	0.167	-0.014
Shawn Green	10.30%	9.80%	-0.005	0.248	0.180	-0.068	10.60%	0.008	0.193	0.013
Randy Milligan	16.90%	18.40%	0.015	0.181	0.121	-0.06	17.50%	-0.009	0.135	0.014
Tim Raines	12.80%	13.00%	0.002	0.151	0.105	-0.046	11.70%	-0.013	0.077	-0.028
Rusty Staub	13.30%	11.90%	-0.014	0.187	0.148	-0.039	11.50%	-0.004	0.166	0.018
Richie Zisk	9.50%	10.10%	0.006	0.185	0.153	-0.032	7.90%	-0.022	0.170	0.017
Jose Vidro	8.30%	8.90%	0.006	0.176	0.149	-0.027	8.00%	-0.009	0.106	-0.043
Roberto Alomar	11.10%	9.00%	-0.021	0.158	0.136	-0.022	14.30%	0.053	0.210	0.074
Dale Murphy	11.90%	10.80%	-0.011	0.227	0.212	-0.015	16.60%	0.058	0.284	0.072
Chet Lemon	9.80%	7.80%	-0.02	0.186	0.174	-0.012	8.50%	0.007	0.156	-0.018
Mike Sweeney	10.20%	7.30%	-0.029	0.200	0.217	0.017	6.40%	-0.009	0.217
Derek Jeter	9.50%	6.40%	-0.031	0.154	0.179	0.025	10.20%	0.038	0.141	-0.038
Adrian Gonzalez	11.50%	6.10%	-0.054	0.223	0.164	-0.059	N/A	N/A	N/A	N/A

No player saw as big a drop in walk rate than Gonzalez. And he declined by a significant margin. In that area, few hitters improved significantly during their age-31 seasons, aside from Derek Jeter, Dale Murphy and Roberto Alomar. A boost in ISO seems more likely, however. As Kevin Mitchell, Bobby Bonds, Eric Davis, Murphy and Alomar have shown, it’s possible to see a bigger gain in this area. The other players in the sample saw small improvements or continued to decline, so it’s a bit of a mixed bag here.

Most players with a similar track record to Gonzalez see improvement after suffering through down years at age-30. Gonzalez, however, saw massive decline in some significant areas. The chart shows it’s possible for him to regain some of his lost power, but more difficult to get the walk rate back. If it was a case of an altered approach, there’s a chance Gonzalez sees a huge gain in his value. If not, he might add some power, but the new approach would prevent him from reaching elite numbers again.

*As some of you pointed out in the comments, I had to readjust the numbers. Gonzalez’s chances at hitting for more power this season increase, but it will be harder for him to regain his walk rate. It’s really a question of approach. If you think his walk rate loss is real, he will be slightly better. If you think he can make a full recover there, he could be pretty good again.