Floyd Mayweather and Marcos Maidana are not just different; they're near-perfect opposites, each possessing the inverse of the other's attributes. The clearest way this manifests itself is that Floyd Mayweather is the world's most masterful boxer, while Marcos Maidana fights like a man who has never boxed before, ever.
Maidana fights like someone who's fought before, sure. He fights like the perpetually angry, pinch-faced kid with a bad haircut and an abusive father who used to beat you up after school as a way of (you realized many years later) lashing out at the world to express his inner pain. He fights with a driven urge to smash a motherfucker. He does not, however, fight like a boxer. While plenty of fighters lack natural smoothness and footwork and grace—making up for it with power punching, or superhuman determination, or, often, just a willingness to get hit a lot—Maidana is unique in that a) he fights at the very highest level of the sport, and b) when he really gets absorbed in his work, he appears to have never even entered a boxing gym or been tutored on the most basic rudimentary elements of "the sweet science" by a trainer. Others may fight like they've forgotten their boxing training, but Maidana spends long stretches fighting like he never received it in the first place.
There is, for example, a punch in boxing known as an overhand right. It's a legitimate punch. A boxing trainer will teach it to you, telling you to bend left and let the right hand loop high, rather than straight, and bring it down on your opponent's head. This is a punch that exists in the Official Handbook of Boxing Punches. It is a risk, because it carries great power but is slow and could leave you off balance should it miss, so it should be deployed only as a finisher on an opponent who is already weakened. It's a strong tool with equally strong drawbacks which demands strategic use.
Marcos Maidana's version of this punch—in a bout against Floyd Mayweather, the world's single greatest boxer, a man who is undefeated and considered close to unbeatable—is just to run up in the very first round and throw the hell out of what can only be called "an overhand right" in the most approximate sense of the term, because Maidana reaches all the way up to heaven and just throws his hand downward with great force, with no deception or defensive positioning or, really, elegance. He just throws the hell out of it like an angry little kid who's been lured into a boxing gym as an outlet for his inner rage, and handed a pair of boxing gloves, and told to give it whirl. He throws it like a bar fighter, like a mugger, like a man who, in all honesty, does not belong in the same ring with a boxer of the caliber of Floyd Mayweather.
And it works! The crazy shit works. Marcos Maidana, on Saturday night, gave Floyd Mayweather the hardest fight he's had in a decade. Marcos Maidana gave Floyd Mayweather a much, much more difficult fight than any number of world class fighters who are, objectively, much better fighters than Marcos Maidana. Marcos Maidana almost fucking beat Floyd Mayweather. How? By doing what a million armchair boxing experts have said (probably while drinking beer) someone should do to Floyd Mayweather: "He should just run right out and the opening bell and just attack the motherfucker like crazy. Just throw everything at him!"
Marcos Maidana came right out at the opening bell and threw everything at the motherfucker. He pushed Mayweather back onto the ropes and just punched, and punched, with crazy and unorthodox and unpredictable and untrained-looking hooks to the body and overhands to the head. Maidana was 17 pounds heavier than Mayweather on fight night, and he used it. He put his body on him, and kept punching, and tried to damage the champ with pure anger. And it almost, almost was crazy enough to work. To be fair, this strategy has a lot to recommend it. For one thing, Mayweather is a brilliant tactical fighter who gets better as the fight goes on. He tends to spend the first few rounds measuring and timing and analyzing his opponent, and then, after deciding exactly what to do, he proceeds to do it, completely shutting down whoever he is facing. He is athletically better than his opponents, and his boxing skills are more precise and refined, but he also is smarter than his opponents, and he is able to employ just the right plan to defeat them. What this means is that if you want to hurt Mayweather, you better try to do it early, because by the later rounds it will be too late.