Carleton: Does a strong finish portend a breakout season next year?

From Russell Carleton at Baseball Prospectus on February 24, 2014:

Over the past couple of weeks, I’ve introduced the idea of estimating a player’s talent level at specific points in time, at least retrospectively, by using a moving average. The idea is that instead of simply assuming that at every plate appearance, a batter could be described by his seasonal average, we might allow that his true talent level varied over the course of a season.

Hitters do grow and develop within a single season, because that’s what humans do. Sometimes it’s obvious that a hitter has figured something out mid-season and that he’s much better at swinging the stick in September than he was in April. Fans and front office types alike love it when that happens, and even if a team doesn’t end up making it to the playoffs, that late-season surge provides hope for the next season—hope that is currently fueling the fantasies of every fan in baseball. Ike Davis had a .326 OBP last year, but in his last 100 plate appearances, he posted a .460 OBP. Jason Castro had a perfectly glorious .350 OBP, but in his last 100 PA, he put up a nifty .450. Ben Revere’s overall OBP was .338, but .410 in his last century of times to the plate. It’s tempting to think that these players—these young players—are finally ready to step up from good, solid players to elite status. After all, the trend line is pointing up, right?

It’s so tempting to want to believe, but like everything else, we need to examine whether it’s a belief based on solid evidence. You want to believe that because he finished strong, he’ll start strong and he’ll stay strong, right? (And in a fantastic feat of cognitive dissonance, you will also assume that the guy who tailed off at the end of the year was just a small sample size fluke that doesn’t mean anything.)

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Originally published: February 24, 2014. Last Updated: February 24, 2014.