You've never heard the term "body weight punch" before? It means the range of motion in your arm is very limited. Hooks and upper cuts are very, very short ranged punches, especially to the body from inside like the one Duffy threw. There doesn't need to be the big wind up where the travel path goes "your face, your shoulder, bicep then fist". It should be a short motion across your body, fist first, driving with your feet. It's a short punch, that's why it's so effective, that's why Tito was always so effective. Watch his previous fight to the fight with Hopkins against William Joppy. Trinidad made a career off of the left hook. Hopkins didn't counter the hook. He threw a right hand off the hook, there is a huge difference.