NEW YORK - A possible bout between retired unbeaten boxing champion Floyd Mayweather and mixed martial arts titleholder Conor McGregor is getting lots of buzz, but one of Mayweather's former opponents said on Tuesday the crossover tilt would be a black eye on boxing.

McGregor has been challenging Mayweather to a fight for months, but the two have yet to reach terms while both have been doing their part to drum up interest with plenty of back and forth in the media.

"It's a joke for boxing if that happens," said WBO super welterweight champ Canelo Alvarez, who dropped a majority decision to Mayweather in 2013.

Alvarez will face fellow Mexican Julio Cesar Chavez Jr. in Las Vegas in May.

Mayweather, who retired in 2015 after compiling a perfect 49-0 record, has said he would require a guaranteed $100 million to make the fight with McGregor happen.

"It is a businessman's fight," Alvarez said during Tuesday's promotion stop in New York for the Cinco de Mayo weekend bout with Chavez on May 6. "I like to fight a serious fight."

But famed boxing trainer Freddie Roach believes the much-hyped Mayweather-McGregor showdown will happen.

Roach, who prepared Manny Pacquiao for the "Fight of the Century" against Mayweather in 2015, said on The MMA Hour show on Monday that Mayweather visited his Wild Card gym and told him he will fight McGregor.

"According to Floyd, yes. He told me he would fight him. Everything is pointing in that direction right now," said Roach, who added he would consider training McGregor if asked.

"I think Mayweather is the favorite, yes, but I wouldn't count anyone out. McGregor knows how to throw punches, hard and fast."

Associated Press