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June 21, 2012

Overthinking It

Melky Cabrera and the Mythical Age-27 Effect

by Ben Lindbergh

If All-Star voting ended today, two of the three starting outfielders for the National League would be repeat representatives. The leading vote-getter, Matt Kemp, made the team last season and went on to be runner-up in the NL MVP race. Behind Kemp is Carlos Beltran, who’s been to six All-Star games.  

But the player who recently displaced reigning MVP Ryan Braun to take over third place has never been an All-Star. He’s never come close to winning any major awards or leading the league in any important statistical category. He’s been a punch line and an afterthought, but before this season, he’d never been one of baseball’s best players.   

That third-place player is Melky Cabrera, who has undoubtedly been one of baseball’s best players in 2012. Even after an 0-for-4 performance against Jered Weaver on Wednesday night, Cabrera is batting .363. He leads the NL with 101 hits, and among NL players, he trails only Joey Votto and David Wright in Wins Above Replacement Player (WARP).

One other stat about Cabrera stands out: like Kemp, who was having a spectacular season of his own before hurting his hamstring, he’s 27 years old. In his 1982 Baseball Abstract, Bill James observed that “both pitchers and non-pitchers attain their greatest aggregate value at the age of 27.” Since then, 27 has been widely regarded as an age of special seasons. Each spring, writers release lists of players primed for age-27 “breakouts,” and fantasy players pick them up, expecting to receive career years in return. If Cabrera keeps this up, he’ll be a perfect example of a 27-year-old player who delivered a dramatically different level of production than he had at 26.

However, it might be premature to proclaim Cabrera the poster boy for an age-27 effect. In fact, there’s little evidence to suggest that breakouts happen more often at 27 than they do at other ages, and good reason to think that calling Cabrera’s 2012 a breakout would be overblown.

Last year, Baseball Prospectus author Derek Carty did a study designed to detect the alleged age-27 breakout effect. Carty looked at all players since 1953 with at least one season of 400 plate appearances or 130 innings pitched, then compared each player’s numbers in each such season to his numbers in the next, grouping the players by age. He defined a “breakout” as a season in which a player outperformed his previous year’s production by at least 20 percent, though he later repeated the study with the minimum improvement set to 10 percent and 30 percent.