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.
Batting average against is calculated as:[1]
BAA=
| H | |
| BF-BB-HBP-SH-SF-CINT |
for which:
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=
| 25 | |
| 125-8-1-2-3-1 |
=
| 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=
| H | |
| AB |
For example, in 2021, Max Scherzer had the best (lowest) batting average against in Major League Baseball among qualified pitchers.[2] Scherzer's BAA for the 2021 season was:[2]
BAA=
| H | |
| AB |
=
| 119 | |
| 644 |
=.185