Originally posted by Galactic Empire Wrong. What about over the top help from safeties playing zone???
If the safeties are over the top and are in range for an INT, then by definition the underneath defender has left the WR.
Safeties help over the top when playing MAN. At least to get close enough for an INT.
It's why the CB/LB is still on the WR/TE.
You need a month of watching NFL Films obviously.
In Zone, safeties close once the ball is in the air. But since the QB knows that, the optimal time to hit the WR is between the zone players, just as the underneath defender stops drifting back.