Versus one-high safety defenses, Four Verticals is very effective because of the pressure placed on the Free Safety.
The ball goes to the call side unless the Safety shifts to that side, then the Quarterback throws to the other A-back.
Here’s how this is run:
Vert versus Bear.
Receivers and A-backs run verticals while the OL slides away from the call.
The B runs his veer path, flattens out, and blocks the first threat off the Playside Tackle.
The Quarterback 5-step drops and throws to the Playside A UNLESS the safety shifts to the Playside… then the Q throws to the Backside A.