Batting average on balls in play (BABIP) is a fairly simple concept to grasp. What it tells us is how often a ball in play turns into a hit (this excludes home runs). If we compare a hitter’s actual BABIP with his expected BABIP (I’ll get in to this in a moment), we can attempt to predict whether the outcomes of his future at-bats will be better, the same, or worse than past results.
How do we go about determining a player’s expected BABIP (xBABIP)? Simple, we mooch off of other people’s hard work. We all know that different types batted balls fall in for hits at different rates. Line drives drop in for hits more often than outfield fly balls do, for example. But some very smart people have sorted through years and years of game data and determined the percentage that each batted ball type drops in for a hit. A line drive ends up as a hit roughly 72% of the time, a ground ball 23% of the time, an outfield fly ball 17% of the time, and an infield fly ball ends up as a hit 2% of the time. These are all rounded numbers, in case you care. My preferred method of xBABIP calculation is Chris Dutton’s xBABIP calculator.
If we apply these ideas to Alex Avila‘s 2010 season, we can conclude that Alex has been fairly “unlucky” on balls in play. Obviously if we’re only looking at the numbers we’re not getting the whole story. Maybe many of Alex’s line drives have been of the soft variety that really only have a 50% chance of ending up as a hit, or maybe his ground balls have been especially weak (illustrations only, I’m not suggesting if this is the case or not). We would have to go back and re-watch all of his at-bats to judge that, but that would take a lot of time so I’ll just roll with the numbers (after the jump).
So far this season Alex has posted a sub-par .261 BABIP. The result of the poor BABIP has been a poor triple-slash line (AVG/OBP/SLG) of .212/.300/.310. For those of you keeping score at home, that’s a .610 OPS, which ranks him 12th out of 15 American League catchers with at least 200 plate appearances. I’ll give you one guess who number 15 is. The xBABIP calculator I mention above tells us that we should have expected Alex’s bat to generate a .331 BABIP. That’s a 70 point difference (nine or ten hits)! If his balls in play fell in at the expected rate, his .212 batting average would instead be .269. That’s still not a fantastic batting average, but compared to what we’ve seen from the catcher position, it would be a welcomed number.
But more important than batting average would be the change it would have made to his on-base percentage and slugging average. The extra hits would increase his OBP from .300 to .348. That’s the difference between well “below average” and “pretty good” (scientific terms, I know). It’s a little bit more difficult to determine how it would affect slugging percentage, but a pretty reasonable way to do it would be to apply his increased hit percentage across the board to singles, doubles, and triples (remember, BABIP does not include home runs). We’re fortunate with Alex because he hasn’t hit a triple this year, so of his ten extra hits, eight would be singles, and two would be doubles. This would cause his slugging percentage to jump from .310 to .375.
These numbers would combine for a xBABIP adjusted triple-slash line of .269/.348/.375. Adding the OBP and SLG components together gives Alex an OPS of .724. This number would be good for 7th among the aforementioned catchers (between John Jaso and Kurt Suzuki). It’s still not a world beating ranking, but it certainly would make me feel a lot better about Alex’s future as the Tigers’ everyday catcher.
The numbers are telling us that we would be right to expect Alex’s production ramp up as he regress up to his mean. Keep your eye on Alex’s BABIP line as the season plays out to see if this is the case or not. I know I’ll watch more closely and make a mental note each time Avila steps to the plate to see if the old-fashioned eye test agrees with the xBABIP numbers or not.