It’s your metric, so you can define it however you like I guess. But I can’t say this makes much sense to me if I’m being honest. When you say that prime is when they were at their best as a fighter, how is that judged? Their record? The eye test? Like, Andrei Arlovski would have like 5 different primes if we’re basing it that way.
This will be a really crude illustration (I had to draw with my finger lol) but you’ll get my drift. Imagine an upside-down parabola, sort of like this:
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This is a fighter’s career. At the beginning there is usually a short period of time where the fighter is very green, but basically that yellow shaded area is a fighter’s prime. It lasts 7-10 years or so usually, although it can be cut short by accidents, injuries and so forth. Usually within that time, a fighter improves and grows, until they plateau—that’s their peak, which is that black circled area in the pic, and it is much shorter—2-3 years or so. How meaningful it is to beat a certain fighter is weighted based on where it falls in that yellow-shaded area.
So would I say that Valentijn Overeem beat Couture in his prime? Yes, I would. Did he beat
the best version of Randy, or what I’d call Randy at his peak? No. But this is what separates those few GOAT-level (or near GOAT-level) guys like Aldo, GSP, Khabib, Fedor— even Usman. They have almost no losses, even in that timeframe on my little graph.
This is basically how I view it anyhow.