Marciano was a great great fighter. But he was getting old when Liston started to make his mark in the division, and he had a chronically bad back that could have 'gone' in the ring at any time.

In my opinion, Liston was the first 'modern' heavyweight. Big, strong and tough, he sort of redifined heavyweight boxing.

Before him, Rocky, Floyd and Ingemar were all guys you imagine in black and white and who you would definitely call 'old timers'. Sonny was the first guy who we can all truly imagine competing in the present day.

When Rocky was old and Sonny was young, I think Liston would have too much for Marciano.