Batting Average on Balls In Play (BABIP) measures how many of a batter’s balls in play go for hits. While typically around 30% of all balls in play fall for hits, there are three main variables that can affect BABIP rates for individual players:

a) Defense - Say a player cracks a hard line drive down the third base line. If an elite fielder is playing at third, they may make a play on it and throw the runner out. However, if there’s a dud over there with limited range, the ball could just as easily fly by for a hit. Players have no control over the defenses they’re facing, and they can only direct their hits to a limited extent. Sometimes a batter can be making good contact, but is simply hitting balls right at fielders. Also, a batter that consistently hits into a shift may have a lower BABIP than a typical player.

b) Luck - Sometimes, even against a great defense, bloop hits can fall in. A batter may turn a nasty pitch into a dribbler that just sneaks past the first baseman, or they may blast a shot in the gap that a fielder makes a diving catch on. Hits can fall in despite the best pitches and the best defenses – that’s just the game.

c) Changes in Talent Level - Over the course of a season, players can go through periods of adjustment. Maybe pitchers adjust to a weakness that a batter has, and the batter starts making less solid contact and getting fewer hits. Maybe a batter is simply on fire for a season, playing at a very high talent level and roping hard line drives all over the field. The harder a ball is hit, the more likely it is to fall in for a hit.

Due to this flakiness, BABIP can dramatically affect a hitter’s batting average. If a large number of a batter’s balls in play go for hits, that can boost their batting average quite high. Similarly, if a large number of balls in play get caught, it can reduce a player’s total offensive value.

If a player has a very high or very low BABIP, it means that whatever the reason for the spike (whether it’s defense, luck, or slight skill), that player will regress back to their career BABIP rate. BABIP rates are flaky and prone to vary wildly from year to year, so we should always take any extreme BABIP rates with a grain of salt.

Context:

The average BABIP for hitters is around .290 to .310.  If you see any player that deviates from this average to an extreme, they’re likely due for regression.

However, hitters can influence their BABIPs to some extent. For example, speedy hitters typically have high career BABIP rates (like Ichiro and his .357 career BABIP), so don’t expect all players to regress to league average — instead, look at a player’s career BABIP rate. And if you want something more exact, try The Hardball Times’ xBABIP (expected BABIP) calculator, available at the top of the page.

Things to Remember:

● Saying a player will “regress” is a tricky statistical subject that confuses many people.  See our section on regression for more info.

● Line drives go for hits more often than groundballs, and groundballs go for hits more often than flyballs.

Links for Further Reading:

Intro to BABIP – Big League Stew

BABIP: What Do We Know? – Beyond the Boxscore

Batting Average on Balls in Play - Wikipedia

BABIP Research – Hardball Times