HR/9 represents the average number of home runs allowed by a pitcher on a nine-inning scale. The statistic is determined by dividing a pitcher's home runs allowed by his total innings pitched and multiplying the result by nine.
HR/9 is a statistic that -- relatively speaking -- is in the control of the pitcher, because defensive positioning plays no factor. Certain pitchers can have success with a high HR/9 rate, as long as they manage to limit their baserunners otherwise -- leading to fewer multi-run home runs. But home runs are so detrimental to a pitcher's cause that this is very rare. Pitchers with high fly-ball rates are more likely than ground-ball pitchers to have high HR/9 rates. However, some pitchers have mastered the art of allowing fly balls but not many home runs.
HR/9 rates in small sample sizes can be very deceiving. And they should also be looked at in the context of the ballpark in which a pitcher pitches, because certain stadiums tend to elicit higher home-run rates.
Watch: Kenta Maeda allows back-to-back home runs, raising his HR/9 rate.
In A Call
"homers per nine"