Much of the most interesting statistical work done over the last 5-10 years has had something to do with the concept of "balls in play." The idea being that pitchers have control over three things: strikeouts, walks, and home runs. (Otherwise known as the "three true outcomes.") Beyond that, most MLB pitchers don't have control over batted balls: the result of those non-HR batted balls is determined by some combination of luck and the defense behind them.
On the flip side, batters (some batters, anyway) do appear to have some control over non-HR batted balls. The players who have the most success with balls in play tend to be speedsters. That makes sense: think of how many times you've seen Ichiro beat out a single, or seen Chad Moeller...uh, let's just say, not beat out a single. Intuitively, it seems like batters should have some control over the balls they hit, and to some extent that may be true.
What I decided to look at this evening was the rate at which Brewers batters put the ball in play last year, and the rate at which they got hits when they put the ball in play. The first stat, which I'll call "BIP%", is largely a function of the type of hitter someone is. You'll notice Russell Branyan is incredibly low--after all, he's 3TO because he relatively rarely puts the ball in play. On the flip side, Brady Clark is quite high, as he doesn't rack up substantial totals of walks, strikeouts, or home runs. The 2005 NL average BIP% was 71.5%, and you see a broad range above and below that number.
The other stat, which is "H/BIP" in the chart below, measures how often a ball in play turned into a hit. This is heavily influenced by luck. While a fast guy like Brady will tend to do better than average, numbers vary somewhat randomly from year to year.
My point in all of this? H/BIP is one way to measure how lucky a player was. Carlos Lee, over his career, turns BIPs into hits about 29% of the time, but only managed 26% last year. If he had merely achieved his career average in his approximately 500 BIPs last year, the 3% difference would've given him another 15 hits or so, increasing his batting average to .290--much closer to his career average.
Comparing a player's seasonal H/BIP to his career H/BIP and you'll get some idea of how that player will perform next year. If you don't have much of a track record to measure a player against, the league average will do: the 2005 NL average H/BIP was 29.5%, though that includes pitchers, so the position player average is somewhat higher. Groundball hitters tend to have higher H/BIP rates than do flyball hitters.
I've included in the table below all position players who got 50+ ABs for Milwaukee last year, as well as Corey Koskie and Gabe Gross. "Car" means "career"--the last two columns are career averages, which are much more useful for guys like Jenkins, Miller, and Lee who have been around for a while.
|First||Last||05 BIP%||05 H/BIP||Car BIP%||Car H/BIP|