October 1, 2012
When Do Players Stop Developing?
"He just needs another year."
If you cheer for a team that didn't quite perform up to expectations this year (and even if you cheer for a team headed to the playoffs), you've got a guy or two like this on your team. He has so much promise; it's just that he hasn't quite fulfilled it. You rationalize it by saying that he's young—well, young-ish. He just needs time.
Every year, there are a handful of guys who take that big step into stardom that we'd all assumed they would for years. After a few seasons of growing pains, Alex Gordon quietly went from disappointing prospect to a very-good-but-not-great player. It’s the tantalizing prospect of another Alex Gordon that makes some fans (and teams) hold on and hope. And a lot of times, it doesn't happen.
But when should a fan or a team give up hope for further development?
Warning! Gory Mathematical Details Ahead!
But we will make do. I isolated a group of players who had at least 100 MLB plate appearances in each season from their age 24-season through their age-31 season. I searched between 1993 and 2011, leaving me with a sample of 168 players. This adds another layer of selectivity. We know that players who debut earlier (at age 24, for instance) tend to peak a little later than their peers. This is in addition to the fact that these players were apparently developing well enough to keep a steady job over the years.