Okay, here is a good learning experience I had right after football practice in college. I have been training in boxing since I was 12, and during my freshman offseason of college football I trained in L.A. boxings MMA and Boxing classes. It was the perfect off season cardio workout for football plus getting to do some good fighting.
One day after some off season drills one of the middle linebackers who was a senior decided he had had enough of the cocky ass freshman in that which I admit I was. So here we go a very good example of a guy who can not fight, but is well conditioned. He was about 5'11 and around 235, all muscle. I'm 6'1 about 215 at the time, I played safety.
This guy spears me, and when I say spear, he football de cleated me and I landed head first. I had no ability to get out of the way, it was just super fast. He started to get on top of me and proceed to kick my ass, problem was when he was punching me he was very wild and he was just doing mild damage to me, more of a frustration to me then anything else. The fight turned about 10 seconds in when I used the one thing that no non trained fighter is ready for......I square hit him in the face, nothing fancy nothing glamorous I was just on my back got a chance and flushed his chin with my right. That was long enough for me to get him off of me and for me to get standing. Then of course he rushes in to spear me again, but now I have entered fight mode and I simply stuck my knee into the top of his head and let him knock his own self out by running into an immovable object. Thats it fight was over. Moral of the story is, just stay calm, and just remember he can't take the punches that you can dish out. Nor can he control his emotions the way you can.