Not sure about a champion, but there was a guy who held the shot put world record and became a boxer...I'll remember his name sooner or later. He was American I think
Your talking about Jack Torrance, But he wasn't a professional athletic. Bill Nieder & Paul Anderson were others, Too Tall Jones was a pro football players, as was Charlie Powell But neither of them became Champions. Yes, Anthony Mundine fits!
I don't know about professionally, but I believe before boxing, Valuev played water polo, discus throwing and basketball. (Russian midget bowling also, I think)
Sergio Martinez was a professional at both cycling and soccer...not elite level...but pro (as in paid to do it).
a couple of athletes have tried their luck at boxing but when they saw what was involved and what a real sport like boxing :yep:think is all about they either quit or got clobbered
Vitali as well, with his kick boxing background. It's more impressive if you were a pro in a non-combat sport though I reckon.