A fight between Floyd Mayweather and UFC lightweight champion Conor McGregor would be a "circus" and a "farce", says boxing great Oscar de la Hoya.

Ireland's McGregor, 28, claims he has signed his half of a deal to face 40-year-old Mayweather, who retired unbeaten in 2015 after 49 fights.

The American has said there is a "90% chance" he will take on McGregor if he returns to the ring.

"Success in one sport doesn't guarantee success in another," said De la Hoya.

The former six-weight world champion, who lost a close points decision to Mayweather 10 years ago, added: "It's not like McGregor would be fighting a good fighter, let alone a mediocre one - he would be fighting the best.

"It looks more and more likely that the circus known as Floyd Mayweather v Conor McGregor will be coming to town in the near future.

"One group will eventually be left to make sure this farce doesn't occur: We, the fans, who are the lifeblood of our sport.

"I fully understand the initial attraction from any fan of combat sports. McGregor is almost certainly the best pound-for-pound MMA fighter. Floyd is Floyd - the most dominant boxer of his time.

"Let's be clear, these are two different sports."

In an open letter posted on Facebook, De la Hoya, who retired in 2009, wrote: "My interest is in the health of boxing as a whole. Our sport might not ever recover.

"To use a bit of an extreme analogy, I happen to be a pretty good golfer. Would I be able to compete with Rory McIlroy, Jordan Speith or Sergio Garcia? Of course not. Nor would I think to try."

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