Oscar De La Hoya says it would be "an embarrassment for boxing" if Conor McGregor was allowed to step into a ring with Floyd Mayweather Jr.
UFC star McGregor has repeatedly called out five-weight world champion Mayweather Jr., despite having no boxing pedigree.
Mayweather Jr. has hinted he is ready to come out of retirement to take the fight, telling ESPN a deal was "very, very close" earlier this month, but De La Hoya insisted that would be a mistake.
"Boxing is boxing and MMA is MMA. They're two separate sports," De Le Hoya, who lost a split decision to Mayweather Jr. in 2007, said.
"It would be a joke, it would be an embarrassment for boxing if an MMA fighter were to go into the ring. It would be a no-contest. It would be the same thing if a fighter went into the Octagon, it would be an embarrassment for MMA."
De La Hoya claimed that if McGregor is serious about his boxing ambitions, he should start at the bottom and work his way up to a shot against Mayweather Jr.
"If McGregor gets inside a boxing ring, he'll get outclassed easy. McGregor has never fought a boxer, ever in his life," he said.
"In all seriousness, he should start off by fighting an amateur boxer, win a few amateur fights, maybe go on to win the Golden Gloves or something, and then when you turn pro he should fight a four-rounder, [in] which maybe he'll get beat.
"But he should get experience in boxing and then call out the best. You cannot be calling out a top fighter in boxing right off the bat."