IF Floyd Mayweather loses on Saturday it will be one of the most shocking results in sporting history.

Few observers are predicting that Marcos Maidana, the Argentine bullet master, will be a threat when they collide for the second time this year in Las Vegas. Their first encounter was better than expected, as Maidana bullied his rival early, and landed almost as many punches over the course of the 12-round distance. Mayweather, for the first time in many years, was put under pressure. However, there were no real doubts about Mayweather’s supremacy at the final bell.

The rematch – again hosted in Floyd’s MGM Grand back room – is expected to be a more straightforward exercise for the champion. Mayweather knows his rival, has superior skills, and will be exceptionally confident of scoring his 47th win.

“The first few rounds were exciting last time and then I turned it around in the second half,” Floyd explained about part one. “I expect to throw more combinations this time. I won the first fight, it’s up to him to change. The champ can make adjustments and I can be especially smart about it. Nobody can solve the May-Vinci code.”

A similar confidence oozed from Ezzard Charles when he agreed to fight Jersey Joe Walcott for the third time in 1951. Then the world heavyweight champion, Charles had decisively beaten Walcott in their opening two bouts and the third contest appeared to be going the same way until round seven. Walcott strolled over to Charles, like an old friend, and unleashed a stunning punch that sent his rival sprawling. It was a game changer, a jaw dropper, and the fight was over.

The following year – after repeating his win over Charles – 37-year-old Walcott was minutes away from victory over Rocky Marciano before he walked into a thunderous right hand in round 13.

Never expect the expected in boxing, particularly when a puncher, like Maidana, is involved. Be cautious of the form book when an ageing fighter, like Mayweather, is in the final stages of a storied career.

“I’m one of those who trains every day,” Mayweather countered to suggestions he could be beyond his best. “I look and feel strong. I’ve dedicated myself to training. The other day I went 14 non-stop rounds. As I get older I grow mentally if not also physically.”

Roy Jones Jnr was at a similar stage 10 years ago. Everybody predicted that he would have a far easier time with Antonio Tarver in their 2004 rematch. Jones – like Mayweather today – was the pound-for-pound leader and thought to be almost invincible. His struggle with Tarver the first time was largely attributed to him dropping weight following his successful expedition to the land of the heavyweights. The forecast for part two was Jones dominating. He was knocked cold in the second round.

Following that defeat, Jones was never the same again. Age, that relentless leveller, had dulled his reflexes and stole boxing’s brightest star.

Sooner or later, Mayweather will get old. If he’s lucky, he won’t be in the midst of battle when he realises that time has caught up. All it takes is a second. One sudden explosion. Maidana dropped a few clues to suggest Floyd’s moment could be closer than we think. Not enough to back the underdog perhaps, but enough to make the sequel worth watching.