Stf
Stuff grade — projected quality of a pitcher's raw arsenal.
What Stf means
Velocity, movement and how the pitches play off one another, on the 20–80 scale. Says nothing about where they end up — that is the command grade's job.
What counts as a good Stf
Higher is better — roughly 40 is poor, 50 average, 60 good, and 70 or better elite.
Also written
stuff_tool
Source
FanGraphs