At the highest levels, the margin for error is slim in boxing. So, too, is the difference between confidence and overconfidence, as Juan Manuel Marquez learned while involuntarily sitting on the floor four years ago.

Lessons learned in that fashion are not quickly forgotten and so the memory of finding himself upside down while dining on canvas lingers on. To be driven onto your back by Manny Pacquiao is nothing to be ashamed of, considering his punching power and concussive reputation. What is more important than undaunted self-esteem, however, is having a clear  grasp on why this happened to you.

That is the edge Marquez will carry into the ring with him at the Mandalay Bay Events Center Saturday night when he faces Pacquiao in a rematch of their remarkable draw. Much time has passed since he was knocked down three times in the opening round only to rise and battle back from the brink of unconsciousness to draw even in a fight many people felt he’d won, but the hard lesson from it remains fresh in Marquez’s mind.

Both are different fighters today. Pacquiao is clearly improved, no longer a left-hand obsessed wild man who only moved his head when looking down at a fallen opponent. Marquez, at 34, may not be all that he was four years ago but he remains a formidable counter puncher and superior technical boxer as well as a wiser man than when they last met. The latter may prove to be the most important.

Regardless of how things end up, one thing is sure. This time he will be on the right side of the thin line between confidence and hubris. He will still have faith in himself to be sure but he will also respect who, and what, is standing in front of him as well.

“I was angry when I saw him on the canvas three times because he was so confident,’’ said Marquez’ long-time trainer Ignacio Beristain. “He was too relaxed in the first round…I was thinking to myself this is not the way he’s supposed to be fighting because, I mean, he seemed too relaxed and knowing Manny Pacquiao, he is like a wildcat. He throws punches from everywhere.

“This happens because sometimes fighters start listening to people. They get close to you and say ‘Don’t worry. It’s going to be an easy fight. You can win this fight. You can knock him out.’ Every fighter faces that. I told him when he got back to the corner (barely), ‘I told you! I urged you not to do what you were doing. So please get back to the plan that we had and everything is going to be fine.’ Everything was going fine except he was so loose it was like he had an invisible opponent in front of him. That’s what cost him the three knockdowns.’’

At the time, Pacquiao was not viewed as the boxing phenomenon he is today. Widely considered among the top three pound-for-pound fighters in the world, he was seen then as a one-dimensional fighter who could punch with left-handed power but who could have his right arm amputated and still suffer no significant change in his offense.

Trainer Freddie Roach has worked hard with him to expand his repertoire and their labors have born fruit. Still, in the end, that left hand and the speed with which it is delivered remains his most potent weapon. The only difference is this time it is a weapon that will be treated with proper respect by Marquez.

Not paralyzing respect that borders on daunting fixation but rather a professional respect that accepts that it must be watched warily at all times.

“I was connecting well in the first round and I was confident,’’ Marquez (48-3-1, 35 KO) said. “I thought it was going to be an easy fight. But, whoa, I got a surprise that it wasn’t.

“He got me with three good punches. I went down three times. But I also got up. Everyone knows I won the fight. He won that round and maybe one or two more. But I won the fight.

“This time, obviously, I won’t be so (over)confident. I’m going to be around from when the first bell rings until the end of the last round. I’m going to be alert. I’m going to pull in all my senses. Everything is going to be in the ring. It’s going to be a totally different fight.’’

It had better be because if Marquez allows Pacquiao (45-3-2, 35 KO) to dominate the opening minutes again he may not escape defeat so easily. This is something he and Beristain understand and something Roach believes will return Marquez to the tight defense and quick counter punching style he has seemed to abandon in several recent fights.

There are those, and secretly Roach and Pacquiao are two of them, who believe perhaps that stylistic change has not been so much to make him more marketable, as Marquez and promoter Oscar De La Hoya claim, but more a result of the ravages of age on a boxer who has been in more than a few wars as well as one Mexican (and Filipino) standoff.

If the latter is true then reining in his confidence will not be the only thing Marquez must do to successfully defend his WBC super featherweight title and lay claim to the RING magazine belt at 130 pounds. With age comes experience but it also brings slower hands and reaction time.

Marquez understands this, which is why he labored through three months of training in Mexico City to prepare himself, working with a host of left-handed sparring partners he did not have before their first fight and running each Saturday up a winding mountain trail into the clouds above Mexico City’s thick smog. There he thought about more than his fitness. He thought about mental preparation and of a night nearly four years ago when he found himself on his back as much because he thought such a thing was impossible as for anything Manny Pacquiao brought to the arena that night.

“After that first round I made some adjustments and I had to make them,’’ Marquez admitted. “It’s been four years now. Manny Pacquiao has become better and I have become better. It’s going to be a totally different fight.

“I can tell you I’m going to be into the fight. I’m going to be concentrating. It’s going to be a hell of a fight. My age won’t be an issue. I can tell you that right now.

“This rematch is coming at the right time. I’m stronger. I think I have more speed. I know Manny Pacquiao’s left hand is like a bullet. It’s very powerful and fast, but I’m prepared. I’m ready for that.

“I learned you have to be alert from the first round all the way to the end and that you never take anything for granted. I clearly learned from that fight. I learned you have to be into the fight 100 per cent every round.’’

Whether knowledge alone will be enough to hold off both Pacquiao and the calendar, which is as much Marquez’s enemy now as his Filipino challenger, will be revealed on March 15. Whether his skills and a new found respect for Pacquiao can counter balance his opponent’s fast hands and annihilating punching power not even he knows for sure but there is one thing he is sure of. He’s sure that when the first bell sounds this time he will be ready for whatever Pac-Man is packing.

“What can I tell you?’’ Marquez said when asked who the better fighter is. “I’m a better fighter. I’m a more technical fighter. I’m in better condition. I proved it in the first fight. I promise you I won’t disappoint you guys.''

Or himself.