I thought I would start with a stat that is slightly more obscure than, say, WAR, but is both useful and extremely relevant: BABIP. BABIP stands for Batting Average on Balls In Play, which is a measurement of how many non-home run “balls in play” end up as hits. In other words, the stat provides a numerical measurement of how many balls put in play by a specific hitter end up as, for example, seeing-eye singles versus ropes straight to the center fielder. The numbers factored into the BABIP equation include strikeouts, hits, home runs and fly outs (I cannot BELIEVE I’m doing this, but here is the equation below, courtesy of FanGraphs).
BABIP = (H – HR)/(AB – K – HR + SF)
“The numerator is the number of hits minus the number of home runs and the denominator is at bats minus strikeouts and home runs with sacrifice flies added back in.” – FanGraphs
There are three major on-field factors that influence BABIP: defense, luck and talent. If the batter is facing a more skilled defender, perhaps one withs faster reflexes or a stronger arm, then the ball in play might become an out rather than a single. The luck of whether a batter hits into a shift, for example, or hits a ball slightly out of a fielder’s reach, is also a factor. And, of course, talent-based factors such as exit velocity and the ability to hit both sides of the plate also play a role in BABIP.
BABIP is a difficult stat to use on its own because of these uncontrollable factors that go into whether or not a ball in play ends up as a hit. Therefore, BABIP is best used in context with a given hitter’s average BABIP over many at-bats. Because the league BABIP average is .300 for a hitter, it is safe to say that a player whose career average BABIP is significantly above .300 is especially skilled at turning contact into hits. Whereas an altered BA over the course of a few weeks most likely signifies either a slump or a streak, the fluctuations of BABIP over a few weeks or a month could be the result of bad luck or good defense rather than talent.
The BABIP stat also exists for pitchers, but requires about a season more of stats to calculate than would an accurate career hitting BABIP. Pitching BABIP is also much more reliant on the pitchers’ team, as his own defense plays a significantly higher role in his BABIP.
Interestingly enough, both Jose Altuve and Aaron Judge, two vastly different players in terms of build, position and overall strengths, boast the third and fourth highest BABIPs in the Majors right now, respectively (behind Chris Taylor and Ben Gamel). Judge is a dominant outfielder and loping power-hitter; Altuve is a small and quick, but still boasts 15 home runs and a .367 season BA. It is likely that Altuve’s speed and Judge’s power (exit velocity) produce similar BABIP results.
In other words, there is more than one way to put balls in play.