Berbick beat Thomas but this isn't important in this case because Berbick's chin was much more better than Ruddock's.(Berbick went the distance with the 100% prime Holmes and this looked impossible before their fight) Only the prime (maybe the strongest version) Tyson and Mercado( when Berbick was absolute green) could knock out him. Ruddock'chin always looked vulnerable when his opponent was dangerous (Smith,Tyson,Lewis,Morrison) and the prime Thomas could fight. Another question Ruddock proved incredible heart against Tyson and Smith.