They blitzed his blind side and the running back Tanner is faking to is on the opposite side. They are overloaded so the line can't get the blitz. The running back can't get it since he is on the opposite side. The only way not to get a sack is hand it off. Utah was able to take that risk because the running game is not a threat. In Shotgun tanner could see the blitz and dump it off to the vacated area.