His chin has improved as he's gone up the weights, thats the only explanation as he got knocked down by a jab early on in his career but then was able to take flush shots from Morales and Marquez.
Being floored by that jab has nothing to do with chin, it's purely about balance. James Toney has one of the greatest chins in history, and he was technically knocked down by a tame clip from Roy Jones. Not every KD reflects on a fighter's chin.
Both Hatton & Pacquiao have very good chins, maybe not in the Lamotta mold but certainly not in the Lewis mould (just joking LL fans)
True. Sam Peter was a natural fully-fledged powerpunching heavyweight and Toney's peak was at mw 15-20 years ago. Toney-Peter I is cast-iron proof of Toney's all-time great powers of resilience.
Pacquiao definitely has a better chin than Hatton, but whether it will be better up at 140 we do not know.