SCOTTISH fight legend Jim Watt has backed Manny Pacquiao to go out with a bang in Sin City.

It is less than 48 hours before the Filipino will go head-to-head with Floyd Mayweather at the MGM Grand in Las Vegas - and already the hype has reached boiling point.

Billed by some as the biggest boxing bout ever to be held, the eyes of the world are watching the two seasoned athletes step into the ring in a battle for supremacy.

American Mayweather is the elder of the pair at the ripe age of 38, but it is the future of his 36-year-old adversary that is making Watt believe Sunday morning's showdown could belong to Pacquiao.

Much of the talk prior to this clash of the titans has come from his camp ahead of the massive payday for both men, and the former world lightweight champion has a suspicion it could be the Filipino's last.

"One of the things that surprises me about this fight is that the public have been screaming for it for years, but the fighters haven't been screaming for it," said the Glaswegian.

"Suddenly, Manny is screaming for the fight, Manny is taking the short end of the purse [£66m against his opponent's £100m], he's bending over backwards in every department to get it made.

"Manny has agreed to everything. Why? I've got a slight little thought in the back of my mind that this could be Manny's pension fight. It doesn't mean he's just in it for the money, it might mean the opposite.

"It might mean this is the last time we are going to see him in a boxing ring, so he's going to give it every last ounce that he has. If it is his pension fight, it doesn't detract from the fight."

Money will obviously be a factor in Pacquiao's motivation ahead of this dust-up, but his background hints at a more noble cause.

Raised in Kabawe in the Philippines, the boxer still resides in his homeland and is even a congressman in his country's House of Representatives.

And while 'Money' Mayweather will have his eye on the cash prize, Watt claims his opponent's pride for his nation - and himself - may just get him through.

He said: "One of the big differences between the two fighters is that Manny boxes for a nation, for his people.

"Floyd has a huge ego, boxes for himself and for the money. He even calls himself 'Money' Mayweather, so that pretty much sums him up. In the last few rounds of a really hard fight, when fighters sometimes need something just to give them that extra spurt, boxing for your nation will give you that rather than boxing for your money or your ego."

Watt is also clear on how he feels the perceived underdog will come out with a bark and a bite.

"I don't think Manny can change," he said. "When Freddie Roach [his trainer] got hold of him he was like a left-hand happy, crude southpaw.

"But about five years ago, Freddie had him as the perfect fighting machine, he was terrific then. He looked like a force of nature.

"All the major changes are in place. I don't think he's going to change any more for this one fight. He's 36, what he's doing has been working most of the time.

"I just think he's going to set a pace, he's going to do it on work-rate, and all-out aggression."