..Force equals mass times acceleration. I don't know if Washington players are generally bigger than USF players or how much faster they are but the opinion most fans have are that p5 teams who are ranked are generally going to be full of players who are bigger/faster/stronger than a g5 team that is not ranked. A player will feel the increase of force with each collision then multiply that by the hundreds of collisions that will occur over the course of a full game. You will be affected by it. Also, when you're going up against an opponent who is generally bigger/faster/stronger, you have to really over-extend yourself with your effort to try and match up which makes you vulnerable to an increased potential for injury.