STAMINA is the key, While others are half dead by the 5th, 6th round, Mayweather still has plenty in his tank.
That's one of his secrets. He drags matches to the last rounds where players are half dead, while he always does his marathon-kind of training with his army of bodyguard/slaves whatever. You will find plenty of his videos on youtube where he is simply running on the streets with his men in the middle of a night. So, he stays in good breath even in his last rounds.
Look how mike tyson started losing following his undefeated streak. Later on, it become evident that he had power, strength etc but lacked stamina. So, to make him lose, you have to survive the first few rounds. He would be half a man after the 5-6th round, so it would be easier to defeat him then.
I don't know why boxers don't focus on this key aspect of the game. Skilll, talent doesn't matter much in the last rounds when you can barely stand on your feet
