PU%
Pop-up rate — share of batted balls hit straight up (infield flies).
What PU% means
Effectively an automatic out — pop-ups are converted well above 95% of the time. For pitchers a high rate is a genuine skill; for hitters it is a mistiming flag.
What counts as a good PU%
Lower is better — roughly .120 is poor, .080 average, .050 good, and .030 or better elite.
Also written
popup_pct · pop_up_pct · infield_fly_pct · popup
Source
Statcast