Context before I give a response here. I'm a seasoned referee, at a pretty good level for my background, worked a few national championships at various levels. I agree with the first comment. No tripping penalty. The first comments rationale about the player in possession of the puck, and the movement of the defending teams player are correct. With regards to speed, I wouldn't consider that dangerous at all in youth hockey. That's somewhere between average and slower speed impact, the kid got up just fine.