Fedor is an amazing Martial Artist but it's difficult to attribute his losses only to being "past prime", because the reality is that in his 3 first losses he faced 3 of the best fighters he had faced until that point. Big Foot, for example, was the type of fighter Fedor wasn't used to dealing with. Most "giants" Fedor fought were very limited. Big Foot was a black belt in judo and BJJ and quite solid in terms of wrestling and striking. You add that to his size and you have a type of monster Fedor had never dealt with before. So it's quite hard to say what would have happened a few years earlier, since we've never seen him face someone like Big Foot.
Also, keep in mind Fedor still looked quite good after those losses. He still beat the crap out of a few low level MMA fighters and looked pretty strong and fast doing it. Certainly, not his absolute best, but lets not pretend the reason he lost had absolutely nothing to do with how good his opponents were. He looked hopeless against the fence in his fight against Henderson, but he didn't look hopeless when he went back to fight cans.
Martial arts experience is also something very difficult to assess. A guy like Wanferlei Silva, for example, has had hundreds of brutal gym wars in brazil. Are you qualified to say that, all things considered, he didn't actually take more punishment than Fedor? How can you evaluate how beat up Fedor was compared to other fighters? By the time he faced Hendo, Hendo's body was already super fucked of for several serious injuries and numerous fist wars. How can you be so sure that at that point Fedor had actually taken more damage than Hendo? You just have no way to know. You want to believe he did, but your beliefs really mean nothing in a discussion where only facts tell the truth. And you don't know the facts. Having a bunch of Sambo fights really doesn't mean you have taken that much damage. Plus, you gotta consider the quality of his opposition.
