In the game of making predictions, fantasy gurus are increasingly calling upon peripheral statistics to support their claims.

Peripheral statistics generally come from analysis of how a ball is put in play (or not) in relation to the outcome of the play. Perhaps the best known is batting average on balls in play, or BABIP, which measures “the number of batted balls that safely fall in for a hit (not including home runs).” BABIP averages are compiled for ground balls, line drives, and any number of other splits.

BABIP is most often invoked to estimate luck. A batter hitting lots of line drives and not getting hits is supposedly due for a positive correction. Likewise a pitcher getting ground balls and not getting outs.

Thus, Tristan Crowcoft recently used two BABIP averages to tell owners not to give up on Kevin Slowey:

Kevin Slowey’s BABIP numbers very much support his case as a big-time buy-low candidate. Both his .357 BABIP on ground balls and .833 BABIP on line drives were noticeably higher than the league averages…

Going many times better, A. J. Mass processes so many peripheral stats in his recent Hit Parade column that he can’t even reveal what they are:

Next, we take the velocity [read the column] and tweak it according to a complex formula based on each hitter’s skill set, determined by a combination of stats that measure patience at the plate, ability to put the ball in play, power potential and speed.

If he told you the formula he’d have to kill you.

How much do I care about BABIP? Not much.

First, these analyses often reveal the obvious. I’m keeping Kevin Slowey because he pitched well last year and because he has sterling minor league numbers, not because he has good peripherals.

Second, these analyses rely upon the premise that the player will continue to produce (or give up) the same types of hits. Your slumping star’s line-drive BABIP may return to the league average over time, but that means nothing if your slumping star hits fewer line drives. The correction you expect won’t have any effect. The market can stay irrational longer than you can stay solvent.