A bit of context, Makhmudov was already 25 years old and had alreaady stopped Nistor one year earlier, Vianello was only 20 years old. Vianello's chin was actually pretty good in this one, he recovered from the beating he took in the first round and tried to fight back durning the 2nd and 3rd round, before the cut stoppage. Makhmudov has drropped/hurt guys who are known for their chin (Nistor and Rice for example), with every power punch he lands clean, so Vianello seems to have a pretty good chin. That lack of power to keep Makhmudov at bay is a bit concerning, but he was only 20 years old, moving a lot and not setting his feet to avoid his bombs. I'd still like to see Vianello vs a durable opponent, that would tell us more about his power/potential lack of power.