Matt Kemp’s Bad Season Not That Unusual

A player’s peak age is generally considered to be somewhere between ages 26 and 29, and during this stretch, it is reasonable to expect a majority of players to perform at the best levels of their careers.  This is the point at which they have gained experience and wisdom but have not yet begun to see their physical skills decline, creating the ideal combination of youth and maturity.

That doesn’t mean things are always rainbows and lollipops for everyone, though.  For Matt Kemp, his age-28 season was a combination of extended stays on the disabled list and a fairly miserable performance when he was able to play.  Rather than living up to his earlier billing as one of the game’s best players, Kemp regressed heavily, and now faces questions of whether he can return to his prior glory, or if this year was an indication that his body is breaking down prematurely.

There’s some good news for Kemp and the Dodgers, however; age-28 regressions are actually pretty common, even for good young players who had established themselves as high quality players at a young age.  And in most of the cases, the guys who took a year off from hitting well bounced back to perform at a high level again.

To show the extent of the drop-off, I looked for players who had been productive hitters (100 wRC+ or better) from ages 25-27, and then had an age-28 drop-off of at least 30 points in wRC+ from their 25-27 average; for reference, Kemp’s drop-off was 36 points, from 139 to 103.  I found 12 such players over the last 30 years, including some of the biggest names in baseball.  Carlos Beltran had a similar down year at age-28, as did Shin-Soo Choo, Jacoby Ellsbury, and Alex Rios.  Among non-active players, we find pretty interesting names like Jeses Barfield, Jason Bay, Andy Van Slyke, and Jose Canseco.   This isn’t a list of guys who just washed out of the league at a young age.

Name 25-27wRC+ 28wRC+ 29wRC+
Jose Canseco 147 101 134
Shin-Soo Choo 142 106 131
Jason Bay 140 93 133
Andy Van Slyke 131 96 133
Jesse Barfield 131 99 116
Bobby Higginson 128 90 131
Carlos Beltran 126 96 148
Jacoby Ellsbury 119 84 113
Alex Rios 117 77 109
Felix Jose 116 72 112
Nate McLouth 115 70 92
Austin Kearns 107 70 78

In fact, in their age-29 season, the 12 players nearly hit as well as they did before their collapse.  In their age 25-27 seasons where they performed well, they combined for an average wRC+ of 126, making them 26 percent better than the league norm in those years.  In their miserable age-28 seasons, they averaged an 88 wRC+, making them 12 percent worse than the league norm.  This is roughly the equivalent of the difference between replacing Prince Fielder (in 2013) with Matt Dominguez.  But then, at age-29, they averaged a 120 wRC+, and every single hitter on the list got better, with 10 of the 12 improving by at least 20 points of wRC+ in the next season.

In a few cases, the down year immediately preceded a season even better than the ones that had come before it.  Carlos Beltrant went from a 126 wRC+ to a 96 wRC+ and then bounced back to a 148 wRC+, which stood as the best mark of his career until 2011, when he put up a 152 wRC+ following another down year.  The two best offensive seasons of Carlos Beltran’s career have come in the seasons following his two worst.

It wasn’t just Beltran either.  Bobby Higginson went 128/90/131.  Andy Van Slyke went 131/96/133.   Shin-Soo Choo (142/106/131) didn’t quite get back to his 25-27 performance in his age-29 season, but he then went on and posted a 151 wRC+ in his age-30 season, so two years after his collapse, he posted the best offensive season of his career.  Likewise, Alex Rios also had his career year after turning 30, but it should be noted that there was another disaster season mixed in there as well.  But his age-28 flop certainly didn’t portend the end of his productive days as a hitter.

Even the two players on the list who didn’t get at least 20 points of their wRC+ back immediately still rebounded down the line, even if that rebound left them as role players.  Nate McLouth took four years to become an average hitter again, but his 2013 season was strong enough to earn him a two year contract with the Nationals this off-season.  Austin Kearns had two miserable seasons at 28 and 29, but then became a useful part-time option at ages 30 and 32.  Neither one was able to consistently get back to their prior levels of production, but they bounced back for short stretches at least.

And let’s be honest: Matt Kemp has a lot more talent than Kearns or McLouth. The guys who hit like Kemp did, and then regressed down to being league average hitters, almost all bounced back to become terrific hitters once again. Kemp’s injury history absolutely is a concern, and his declining defensive skills means that he’s going to have to hit at a high level in order to justify his salary, but there are plenty of reasons to think that Matt Kemp is going to hit again, and probably in the not too distant future.

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Dave is the Managing Editor of FanGraphs.
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But to what extent were injuries were responsible for each of the age-28 declines is the hard question.