Usually, we expect players to follow a more or less expected curve of decline when they hit their 30s. Obviously everyone is different, but baseball is a young man’s game, and father time comes for us all. Research by Jeff Zimmerman in 2013 showed that hitters don’t even tend to peak nowadays: on average, they perform at a plateau upon reaching the majors, then they decline. Take the wRC+ aging curve for a few different time periods, for instance:
We often talk about a player being “in his prime,” but primes are probably younger than many (or most) people think. In this era, 26 is really the beginning of the average hitter’s offensive decline. Which brings us to Ian Kinsler, who will turn 34 in June: he’s currently posting what would be the highest wRC+ of his career, and Isolated Power marks in line with his best home run-hitting seasons of 2009/2011. That isn’t particularly huge news: plenty of veteran hitters have ~40 game stretches in which they match close to their prime production.
The real news is that Kinsler is currently going beyond that, showing a few underlying indicators that amount to him turning back the clock. He’s also altered his approach, and the combined forces are helping to drive what is currently shaping up to be his best offensive season since he posted a 123 wRC+ with 32 homers in 2011. Kinsler is probably never going to steal 30 bases again (or maybe even 20), but he’s picking up that slack in his production at the plate, especially power-wise.