Kamaru Usman explains why it's impossible to determine the greatest of all time.

Usman (21-5 MMA, 16-4 UFC) entered the greatest welterweight of all time conversation after five consecutive title defenses. Ahead of him is Georges St-Pierre, who is widely considered not only the greatest welterweight of all time, but arguably the greatest period.

Usman is confident that in his prime, he can beat St-Pierre, but also says each generation coming up is more talented than the other which is why it's hard to compare.

"There's no greatest of all time," Usman said on his "Pound 4 Pound" podcast with Henry Cejudo. "There's greatest of your time. That's what that is: Greatest of your time, not greatest of all time because they're different skill sets. This generation is good at one skill, this generation is good at two skills, this generation is good at mixing it up. Now you've got little ninjas that are 15, 16, 17 years old doing spinning triple back kicks, flips, and all of this stuff. For the longest time, you didn't kick and punch on the same side. Now people are doing that at will like it's nothing.

"Each generation, each time, there's a different champion, there's a different guy that masters their time and they become the greatest of that time. I am a humongous fan of Georges St-Pierre, and I think Georges St-Pierre is great. I think in his time he was the greatest. And me being the competitor that I am, that I was, I think in my time I was good enough to beat him. But that is my opinion. That's not saying that's exactly what would have happened. I'm sure he felt, because he was a dog, he felt he could have definitely beat everybody."

What sparked the discussion is Petr Yan now being considered the bantamweight GOAT after retaining his title against Merab Dvalishvili in Saturday's UFC 333 co-headliner. Yan has only ever defended his belt once, which is why Henry Cejudo thinks he's ruled out of the conversation – for now.