I've never seen it. It sounds like one of those judgment calls; sometimes it's hard to say whether it was really a punch or a slip/nudge that caused a guy to fall. If it was a knockdown, it wouldn't take away from all of Chuvalo's demonstrations of incredible durability, but it would deduct from the legendary nature of his reputation, much like if Marciano had lost the split decision to LaStarza- both guys would principally remain basically the same, but the "never floored/never beaten" marks add a certain legendary quality to their careers.
Those who saw Chavalo vs Bonavenna say 2-1 there was a knock down. I want to see this fight. Based on styles it seems intersting , and the knock down or no knock down debate is something I want finalaity on. Of topic, EPSN Classic aired Ringside on Ali's final chapter. Chuck Wepner, Angelo Dundee, and Bert Sugar were on stage. Brian Kenny was the host. Wepner, Dundee, and Sugar all say it was a clean knockdown, and no one says Wepner stepped on Ali's foot. In addition, host Brian Kenny says Ali was a bit hurt/shaken up. I have to say Wepner is interesting on TV, and can be rather comical as well. I seen Chavalo on camera as well, and his insight is interesting too. Not all veteran fighters get out of the game with their marbles. Who would have thought two guys known for taking punches and mixing it with better fighters would be the voices for the boxing of their time.
In the final replay any astute observer can see Wepner's left front foot rise as Ali's foot slips out from under Wepner's. One can also zone in on Wepner's knee to top of sock area and see this portion get pulled forward as he feels the weight of Ali's foot under his pull away. [yt]TBxAuNEFRJU[/yt]