Not a safety in my mind.
In possession of the ball, the player clearly was in the field of play, where he was contacted. The force by the defense caused the player to go backwards. I did not see any contact that was released. In this case, I think the forward progress was in the field of play. Good call by the side guy.
Had contact been released, can one make a judgment call in US rules that a backwards step by the carrier was caused by a loss of balance due to the defensive contact? If so, it is still not a safety.
