Paulie Malignaggi says Saul Alvarez must use his size to ruffle Floyd Mayweather on Saturday night.
The former two-weight world champion is tipping Mayweather to extend his unbeaten record to 45-0 with a canny points victory at the MGM Grand but says 23-year-old Mexican marvel Canelo can cause the veteran American problems with his size.
New Yorker Malignaggi reckons Alvarez is naturally suited to the junior middleweight division and could potentially outlast Mayweather if the bout is contested at a quick pace throughout.
"Canelo is the first junior middleweight Mayweather is fighting who is a real junior middleweight," Malignaggi told Ringside.
"Canelo is a full-blown junior middleweight, unlike Miguel Cotto, who Mayweather fought who was actually an ex-welterweight and junior-welterweight. Canelo has fully grown into his frame and the curiosity is how Floyd would deal with a legitimate junior middleweight.
"Let's face it - Floyd, as good as he is, can still make the welterweight division but he's making a conscious effort to move up to take on bigger challenges.
"Alvarez has to start fast and use the physical attributes he has over Mayweather and rough him up a little.
"Even if Floyd is winning early in the fight, if he's forced to fight at a pace he's not comfortable with by the bigger man, I'd say the late part of the fight could get interesting. Size matters in the later rounds especially."
However, Malignaggi expects Mayweather to have plenty of plans in place to dispatch his so-far-undefeated challenger.
"I see Mayweather fighting a very careful, calculated fight," he said.
"Mayweather's not stupid, he knows Canelo is strong, bigger than him naturally and is not a guy to play with or take too many chances with. Floyd will get his timing down and win the fight on points without taking too many chances."
Jim Watt, meanwhile, reckons the clash will be a blockbuster and says Mayweather - who defeated Robert Guerrero in May - could be the sharpest he has been in many years.
"If you held a poll and asked who should Floyd Mayweather fight next, Alvarez would be the unanimous decision," he said. "It's a terrific match.
"This is the first time since 2007 Floyd Mayweather has fought twice in the same year, though, so he's going to be as sharp for this fight as he's been for a long time.
"Against Guerrero in May he was sensational and he's building on the sharpness and stamina from that fight - I think he's going to be in the condition of his life here and that makes it even more difficult for Alvarez."