I was given some pointers from a retired military boxer recently.
We went over stances, guards, strikes, etc. He told me his theories on fighting in the ring versus self-defense on the street, and we then went over some good martial arts strategies for facing a boxer. Namely, don't let him break my ribs and take minimal damage while I moved inside his striking range. However, the full details of these points I will not go into right now. Rather, I want to point out one of the most important things I learned from him before even a friendly sparring punch was thrown. Namely, that I knew his power and intent were there before we even took a step towards each other. His guard was tight, his face was mean, and he showed an inherent awareness of why I travelled so lightly on my front foot. He narrowed my options and had no problem with forcing the action. He was more interested in striking my ribs first than my face, claiming if "I can't breathe, well... I can't fight." And believe me, while qi studies may not be a usual component of boxing, the qi was definitely there.
In this instance this was certainly the case.