I'd say he was a good puncher, but not a huge puncher. He looks like a big puncher against outclassed opponents because his reflexes put him in a good position for flush counters. Even in this situation he still needs a few shots. I don't remeber him devastating someone with one shot. I don't see him getting the opening he needs from Mayweather. People are also making a lot of the size difference. Do you remember how much bigger Kostyta was than Zab in the ring? Zab isn't a big welter. It's his ability not his size that have made him competitve at the weight.