I think he was only knocked down once prior to the mayweather fight, you have to look no further than fight to see where Hattons resistance started to go down than the fight mentioned above when he collides with a ring post. Its a simple case of poor lifestyle and an exciting style which caught up with him.
Always thought he had a good chin, just left it in Las Vegas after the Mayweather fight. If you watch the Lazcano fight over you see he gets caught a few times too many and his legs wobble, never noticed that before the Mayweather fight and I watched a good 15 or more Hatton fights prior
Started out with an Iron chin, tzu wollaped and wollaped him. As time wore on his core strength left him through lack of a healthy lifestyle, as a result his punch resistance left him, hence pacquiao`s hail mary punch.
Well I remember Paulie landed a shot and stunned Hatton, Im not sure he was hurt, but it was definately not one of these shots that would have stunned him earlier in his career (before the Mayweather fight)