How can OPB be lower than BA?

Answer 1

You might see a player's OBP (on base percentage) lower than their batting average for a game or two but there is virtually no chance that it would happen over an entire season as a player would have to have an incredibly higher number of sacrifice flies than total of (walks + hit by pitch).

To review ...

Batting average is calculated as (hits / at bats).

OBP is calculated as (hits + walks + hit by pitch) / (at bats + walks + hit by pitch + sacrifice flies).

Example 1: A player has played 2 games and has 8 at bats, 2 hits, 0 walks, 0 hit by pitch, and 1 sacrifice fly.

Batting average is .250 (2 / 8).

OBP is .222 (2 + 0 + 0) / (8 + 0 + 0 + 1).

Example 2: A player has played an entire season and has 500 at bats, 150 hits, 50 walks, and 5 hit by pitch.

Batting average is .300 (150 / 500).

For the OBP to be lower than the batting average, the player would need 129 sacrifice flies ...

(150 + 50 + 5) / (500 + 50 + 5 + 129) = .2997.