Where Is Jason Bay’s Power?

Jason Bay’s status as a prized free agent was primarily based on one skill: his ability to hit home runs. He hit 36 in 2009, and 31 in 2008, cementing himself as one of the games premier power hitters. Indeed, CHONE and ZiPS projected Bay for 34 and 36 home runs respectively, and even the pessimistic FANS saw a 29 home run season for Bay.

Halfway through June, however, Jason Bay has four home runs. With 267 plate appearances under his belt already, that’s a pace for only 13 home runs, putting him on a level with such vaunted sluggers as Melky Cabrera and Pedro Feliz.

It’s possible that Citi Field is part of the issue – only 40 home runs have been hit there all season. Right handers attempting to pull the ball have to deal with a 335 foot left field corner which quickly juts out to 364 foot and then a 384 foot left center power alley. Bay hit 24 HRs to left field last season; through 63 games, he’s hit one.

Let’s compare Bay’s 2009 and 2010, thanks to the excellent data over at Hit Tracker Online

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It’s a sea of red in left field, but no blue to be found. The HR that was classified in left field is close to center field. Bay’s power to left field has simply disappeared. Bay’s ISO to left field is a ridiculous .110 – of the 82 balls he’s hit to left field, only 6 have gone for extra bases. That’s after posting 42 XBH to left in 2009, and 34 in 2008.

To expect Bay to post a ridiculous .466 ISO to left field, 165% of the league average for right handers, for a second time in 2010 would be a mistake even if Bay wasn’t moving from one of the most righty-friendly parks in the league to possibly one of the least. He was about an average hitter to left in his split campaign between Pittsburgh and Boston in 2008 and was well below average to left in 2007. It would be shocking to see Bay put up two of these high octane seasons, especially in his age 30 and 31 seasons.

What we’re seeing with Bay seems to be one of the nastiest combinations of park effects, regression to the mean, aging, and simple poor luck that I can recall a power hitter encountering. It’s certainly possible that Bay has simply lost some of his pop, but right now the most likely scenario is that Bay is working through an extended slump. ZiPS projects him to add 19 more home runs before season’s end, as opposed to the 9 that his pace suggests. It’s too early to dismiss Jason Bay as a power hitter, even if he can’t replicate his awesome 2009.