Floyd Mayweather Jr. will make his return to the ring on May 3rd in Las Vegas. But if the undefeated American decides to go up against Amir Khan, legendary boxer Marvin Hagler wants the fight to be staged in the United Kingdom.

Hagler, who is considered as one of the best boxers of all-time, said that for Mayweather to consider himself as the best-ever fighter in history, the reigning pound-for-pound king should step out of his comfort zone and fight outside the United States.

The former undisputed middleweight champion cited his previous decisions to defend his title in London and Italy during the 1980's, and he insisted that Mayweather should do the same to cement his boxing legacy.

"When I was undisputed champion I always had to fight the number one contender. It made me that much better, made me work that much harder, made me get in better condition. The fighters back in that era, they trained harder and were more dedicated to the fight game," Hagler said in an interview with The Clare Balding Show as reported by Give Me Sport.

SEE: Floyd Mayweather vs Amir Khan Looms, Potential $200 Million Showdown Could Be Finalized With Marcos Maidana Out Of The Running

Mayweather has yet to name his opponent for his next bout, but Khan is considered as the most likely foe of the 36-year-old American, who is coming off a record-setting showdown with Saul "Canelo" Alvarez in September.

The Mayweather vs. Alvarez showdown set the second all-time highest pay-per-view buys with 2.2 million subscriptions, while also recording the all-time highest domestic PPV earnings at $150 million.

When asked if the talked-about showdown between Mayweather and Khan will have the same appeal as the pound-for-pound king's previous fight, Hagler said that it will be an interesting showdown, but it will be more enticing to fight fans if it will be staged in the UK.

"It's going to be an exciting fight," Hagler said. "But what the British people would love to see is Mayweather taking the big step and coming here and fighting Khan on his turf and showing the world really if he is a true champion instead of fighting in his own back yard in Vegas. You need to expose yourself, everyone knows you're a champion."

Aside from Khan, newly-crowned WBA welterweight champion Marcos Maidana is also being considered by Mayweather as his next opponent. However, Maidana's name is expected to be thrown out of the window once his rumored rematch with Adrien Broner is finalized.