BB/9
Walks per 9 innings — command proxy.
What BB/9 means
Lower is better. League average ~3. Below 2 is elite command; above 4 is a problem for most pitchers.
How BB/9 is calculated
BB/9 = BB × 9 / IP
What counts as a good BB/9
Lower is better — roughly 4 is poor, 3 average, 2.5 good, and 2 or better elite.
Also written
bb_per_9