How much does the past affect your opinion on a fighter?

Not really sure how to explain what I mean here but it's just something I was thinking about earlier.

Take someone like Wladimir Klitschko - who has been KO'd three times and been knocked down about dozen. However, the last 7 or 8 years he's been pretty much untouchable. Yet people will still bring up the past when talking about how to beat him, how they rate him etc.

On the other side of the coin is someone like Floyd Mayweather - where there is no blueprint etc. Never officially lost and because of this many see him as pretty much unbeatable, at least in this era.

Also someone like Adrien Broner - who's still only 23/24 whatever but has a couple of debatable wins on his record. I often see people say how Broner is overhyped because he could have lost to Ponce de Leon and Quintero. Despite looking mostly awesome in his last 5 or 6 fights, these marks sometimes still get brought up.


How much do previous defeats, knockdowns, setbacks etc affect the way you rate a boxer and his chances going forward?