Here is the thing about 40 times... they don’t tell you anything at all about players playing speed... so much more goes into playing fast than just 40 speed... reaction times, mental processing, motion fluidity, burst, change of direction, anticipation... ... if you have a lightning fast guy who has to slow up to find the ball, or who has a slow change of direction, or who processes overages slowly... they won’t play as fast as they are straight line... and a couple tenths of a second... even a FULL second speed difference divided over forty yards is almost nothing in most plays... a good angle from even a slow safety can catch most players if they read it fast enough...... but a player that can shift direction without telegraphing the move and who makes fast reads on defenses can be brutal to cover... like the “ slow” jerry rice