There was plenty of contact both ways, but the defender ever so slightly held and impeded Gronk while the ball was in the air, enough to keep him keep him from making the catch.
Since things are pretty quiet today, NFL-wise, until tomorrow night's game between CAR and NO--which I hope is a good game--I'll play along with you.
The
restriction against defensive PI begins only after the ball is thrown, while the restriction against offensive PI starts as soon as the ball is snapped. Actions that constitute offensive pass interference include but are not limited to:
(a) Blocking downfield by an offensive player prior to the ball being touched.
(b) Initiating contact with a defender by shoving or pushing off thus creating a separation in an attempt to catch a pass.
(c) Driving through a defender who has established a position on the field.
Gronk violated at least (b) and (c), as Kam had established his position, did not move, and Gronk
initiated contact (not Kam), by charging at Kam and shoving him with both hands to the ground to create separation, then veered to his left to attempt the catch.
Incidental contact by a defender’s hands, arms, or body when both players are competing for the ball,
or neither player is looking for the ball is NOT PI.
Note 1: If there is any question whether player contact is incidental, the ruling should be no interference.
Note 2: Defensive players have as much right to the path of the ball as eligible offensive players.