Walks per nine innings tells us how many walks a given pitcher allows per nine innings pitched -- using the formula walks divided by innings times nine. BB/9 rate is a solid measure for judging a pitcher's control, though walk rate (per plate appearance, not per nine innings) is the preferred metric by some.
Obviously, a pitcher's goal is to keep opposing batters off the bases -- and a walk does just the opposite of that. If he allows a ball in play, he at least puts the outcome in the hands of his defense -- and luck. But a walk gives the team behind him no chance to help.
Because of this, pitchers with high BB/9 rates tend to struggle. However, there are a few pitchers who can get by with high BB/9 rates because they also record high strikeout totals and keep hitters off the bases.
BB/9 rate carries a strong correlation to WHIP, also known as "walks plus hits per inning pitched" -- one of the standard fantasy categories. Pitchers with low BB/9 rates are likelier candidates to post low WHIPs, as walks comprise half of the numerator for computing WHIP. Conversely, pitchers with high BB/9 rates tend to post higher WHIP figures and, accordingly, are more susceptible to run allowance, higher pitch counts and shorter outings.
In A Call
"walks per nine," "walk rate per nine," "walks per game"