Contact Against an Opponent Out of the Play
ARTICLE 12. a. No player shall tackle or run into a receiver when a forward pass to him obviously is not catchable. This is a personal foul and
not pass interference.
b. No player shall run into or throw himself against an opponent obviously out of the play either before or after the ball is dead.

My comment: He was clearly out of the play at that point. He was on his back, many yards away from the ball and had made no effort to rise (yet). 44 for UVA should have waited, and if Gaines had tried to get up and get into the play, then 44 could have continued to block him. What 44 did was a penalty without the helmet lead. With the helmet lead, he should have been ejected as well.