This story appears in ESPN The Magazine's August 21 Fighting Issue. Subscribe today!
When boxers prepare for a fight, it's a process of daily accretion. They sharpen, strategize, suffer, reveal their own weaknesses, then correct them. And few see the process more than a sparring partner. So what makes Floyd Mayweather so great -- and the overwhelming favorite to beat southpaw Conor McGregor on Aug. 26? For the answer, we sought out boxers who have worked with Mayweather in recent camps where he's been preparing to fight left-handers. Two of them, Zab Judah and DeMarcus Corley, lost unanimous decisions to Mayweather. One, Errol Spence Jr., might be the best welterweight in the world right now. None of them gives McGregor a chance. Here, they tell us why.
The right-hand lead
Why Mayweather's right is the most consistent weapon in boxing
Errol Spence Jr., Current IBF welterweight champ (22-0, 19 KOs): He throws it as a jab, in a way. It comes so fast. A lot of fighters telegraph their punches. He doesn't at all. It's really something that he's just mastered, throwing the straight right and catching guys over and over.
Zab Judah, former two-division world champion: He knows how to throw it, when to throw it, where to throw it, how long to throw it, how short to throw it, how hard to throw it.
Jack Catterall, prospect (18-0, 10 KOs) challenging for a British super lightweight title in October: The way he positions himself, you think there's an opening to land your jab. You think you got your punch, but he does that little shoulder roll and hits you with the right. Or he'll set it up with the jab and trick you into thinking it's an opening -- and it's already a mousetrap that he's set up for the right.
Demarcus Corley, former WBO junior welterweight champion: Floyd throws it like a f---ing snake. He's like a snake that you can't hit, but he keeps striking you.
The inside story on how he breaks fighters down slowly
Catterall: In close quarters, he kind of holds the left arm like a bar in front of your guard. Then comes the stabbing right hand right above the groin. He's getting that shot off well on the inside. I experienced it. It's not a stabbing pain. It's an ache. The more he touches it, the more intense the pain becomes. You're thinking, I need to block this body shot. What do I need to change? You're trying to figure out how he's taking your body apart. It slows you down, slows your legs down, takes energy from you.
Spence: Those little shots have an effect, shooting the jab in your stomach, which he does a lot, or in a clinch throwing an uppercut to your body. That's a big factor when you're using your legs to move forward to try to catch a guy.
Corley: He's not trying to hurt you; he's trying to let you know, "I'm just taking a little bit out of you. I'm going to break you down eventually." That's something Pernell Whitaker used to do.
He trains so hard, he doesn't get tired -- or tired of talking
Spence: I never saw him breathing hard. He always controls his breathing -- and that's an art. A lot of fighters, you see them breathing out of their mouths. Floyd always breathes out of his nose. He fights in the 12th round like he fought in the first round due to how hard he works. He does mitts for 30 minutes, then hits the bag for 30 minutes straight, then goes running, then goes to play basketball.
Judah: When he trains, he lines up like 15 to 20 sparring partners at a time. I've known him since we were amateurs. He's always done over and beyond what the job consists of. You can't beat someone who's not going to get tired.
Corley: He starts talking to his opponent, and that's something that I experienced in the fight and in camp with him. He's saying, "Eat this! Nope! Nope!" He's going to say that in the McGregor fight when McGregor's missing his shots, "Nope! Nope! Hell nah!"
Catterall: You're tired, and he's still fresh. When he sees that, it's kind of like he's appreciating his own work. He's kind of smiling, thinking, I'm bossing this fight, and you can't do s--- about it. He has not knocked you out, but it's like he's enjoying the fact that he's giving you a calculated beating and you can't do nothing.
Don't worry about knockouts, he can still pack a punch
Spence: I've seen him stop guys in the gym with 16-ounce gloves. Bigger guys. He just beats them up. In his young career, you saw how he was knocking guys out. But now he's got hand problems, so he's not turning with it all the way, not putting 100 percent power into his punches. But he can punch hard. That's why a lot of guys, when he hits them, they start backing up or go on defense. They're not just walking through his punches. You haven't seen anybody who's walking through his punches. Even Marcos Maidana started backing up when Floyd started coming forward.
Corley: His power is the quickness of his punches, the placement. His punch placement is so on point, from the outside it looks like he doesn't hit hard. But when he hits you, you feel like, G--damn, I have to regroup now.
Catterall: The one thing I picked up on in sparring was his accuracy, catching the same spot over and over again. He's very cute with his punches, finding the same little spot. I always like to think I work on my defensive game a lot, so I'm like, F---, how does he keep hitting that same spot? But he always manages to find a way.
Inside the shell
Why Mayweather's shoulder roll is unlike any other fighter's
Catterall: When he's backed up, he'll use the shoulder roll. He'll pull and slip the punch, then he'll take a short little step back and he'll pivot. You'll be there still throwing punches. He makes you think he's there, but then he's off all of a sudden. A lot of fighters try to do it, but it's not a style a lot of fighters can adapt to. It takes years and years of practice. But with Floyd, he can even walk toward you in the shoulder roll and use it to attack more.
Judah: Floyd has been doing that shoulder roll since day one. Since the amateurs, that's the only style he's ever done in boxing. He learned it from his dad and his uncle Roger.
Spence: His right hand is to block the hook, and sometimes he'll block the jab with it. His shoulder is to block the straight right. If I throw an overhand hook, he'll roll it and shoot with the other hand. A lot of guys see the shell and jump in and throw a lot of punches. That's when he shoots down the middle with a straight right or hook and catches you with something crazy.
Corley: He's so elusive -- his movement, his reflexes. When you shoot, he twitches his left shoulder up to block his chin so he can't be hit with a right hook. His right hand is already up to catch anything coming from that side. When they say Floyd doesn't have any balls? You got to have balls to stand and catch a punch, come back with a punch, then get the hell out of there. That takes timing, practice and a lot of heart to stand in the pocket and get your shot off.
He commands the ring, even when he's pinned in the corner
Spence: He actually is very physically strong. Even bigger guys can't push him around or throw him around the ring. And you never know what he's going to do. He might stand there and catch it with his elbows or with his hands, shoot something and get out the way. Or he might roll with it and catch you. Or use his legs and slip, slip, slip, and roll around you and make you look silly. You never know.
Catterall: If you have him in the corner or pinned on the ropes, he'll smile at you and wave you on like, "Come on, let's have it." You throw your punches and you might catch him with a shot, but you never seem to catch him clean. He'll somehow just spin off, and you'll feel like you've hit nothing. I believe I've got good timing and good speed, but he has that 1 millisecond where he makes you miss and you think you've got your hand back, but he'll catch you.
A boxing brain
Why Floyd's mind separates him from other fighters
Spence: His eyes are always open. Your mind can't wander; it's a mental workout as much as a physical workout. Fighters throw punches at him, and you see him looking. He moves just enough and never overreacts to a punch. You never see him rattled. When you go back to the corner, he's looking at you, seeing if you're tired.
Catterall: The stuff I was trying to do, within a matter of a round, he'd adjust to it and it'd be time to do something else. Everything I tried, he read it straightaway. His ringcraft is incredible.
Corley: Let's say I catch a person's jab; I'm going to come back with the opposite hand. But for Floyd, his dad and uncle showed him to catch a punch and come back with the same hand. He is the only fighter I know who does that -- only fighter who can, probably -- and the only reason is that he's been programmed from Pampers. He breaks the will of fighters. After a few rounds, you realize it's not what you thought it was going to be. You can't do what you want to do to him. You start questioning yourself. How can I get this guy? What is he doing that I can't catch him?
Judah: He studies your background down to your kids, your wife, who your mama is, who your daddy is. He doesn't watch fights; he prepares for the person. Sometimes when you learn the person, you don't have to learn how they fight.