Batting average against



In baseball statistics, batting average against (denoted by BAA or AVG), also known as opponents' batting average (denoted by OBA), is a statistic that measures a pitcher's ability to prevent hits during official at bats. It can alternatively be described as the league's hitters' combined batting average against the pitcher.

Definition
Batting average against is calculated as:

$$BAA = \frac{H}{BF-BB-HBP-SH-SF-CINT}$$

for which:
 * H is the number of hits allowed by the pitcher
 * BF is the number of batters faced
 * BB is the number of base on balls
 * HBP is the number of hit batsmen
 * SH is the number of sacrifice hits
 * SF is the number of sacrifice flies
 * CINT is the number of catcher's interference

For example, if a pitcher faced 125 batters and allowed 25 hits, issued 8 walks, hit 1 batsman, allowed 2 sacrifice hits, allowed 3 sacrifice flies, and had 1 instance of catcher's interference, the pitcher's BAA would be calculated as:

$$BAA = \frac{25}{125-8-1-2-3-1} = \frac{25}{110} = .227$$

Reference site Baseball-Reference.com more simply defines BAA as hits divided by at bats, as "at bats" for a pitcher equates to the above noted denominator (batters faced less walks, hit by pitch, sacrifice hits, sacrifice flies, and catcher's interference):

$$BAA = \frac{H}{AB}$$

For example, in 2021, Max Scherzer had the best (lowest) batting average against in Major League Baseball among qualified pitchers. Scherzer's BAA for the 2021 season was:

$$BAA = \frac{H}{AB} = \frac{119}{644} = .185$$