Former WBO cruiserweight champion and Sky Sports pundit, Johnny Nelson, believes Mexican superstar Saul 'Canelo' Alvarez is potentially making a big mistake in moving up to the cruiserweight ranks.

Last month, Canelo became the undisputed super middleweight champion with a knockout of Caleb Plant.

Canelo has now captured world titles at junior middleweight, middleweight, super middleweight and light heavyweight.

He's motivated to capture a world title in a fifth weight class.

At the recent World Boxing Council convention in Mexico, Canelo's manager and head trainer, Eddy Reynoso, requested permission to challenge WBC cruiserweight champion Ilunga Makabu, who next month will make a mandatory defense against Thabiso Mchunu.

Canelo's unexpected move is being viewed as significant jump in weight and a dangerous risk. The cruiserweight limit is 200-pounds.

The Mexican star has not fought any higher than 175-pounds, when he moved up to light heavyweight score a knockout of Sergey Kovalev to capture the WBO title. Afterwards, he vacated the belt and dropped down to super middleweight.

Several cruiserweights are already expressing interest in facing boxing's biggest cash cow - including the division's former undisputed champion Oleksandr Usyk - who expressed interest in dropping back to cruiser for a one-off. 

"Canelo could be his own biggest threat. He might be biting off more than he can chew by stepping up to cruiserweight," Nelson told Sky Sports.

"Me, as a former cruiserweight, I'm kind of insulted that this little man is coming up to our weight division. Any worthy cruiserweight will think, 'No, that's not happening!'.

"That's why the likes of Oleksandr Usyk are willing to step back down to cruiserweight to prove this. You'll have a number of cruiserweights like Makabu, who are beatable. But then you have other cruiserweights that Canelo should never beat in a million years. Canelo's biggest threat might be himself."