McGregor was "schooled" by Mayweather, says Lewis
Conor McGregor was "brought to school" by Floyd Mayweather and needs to "stay in his lane", according to former heavyweight champion Lennox Lewis.
UFC star McGregor lasted 10 rounds with Mayweather in his maiden professional boxing match in Las Vegas, as his opponent stopped him to retire with a perfect 50-0 record.
Many had predicted McGregor would barely last a round with one of the greatest fighters of all-time, so he has earned some credit to have stayed the course for as long as he did.
However, the statistics and scorecards back up what was consistently predicted - that he would not have the durability to go toe-to-toe with a master of his craft for 12 rounds.
And, despite his immediate online reaction being to say "I like him even more now", Lewis told BBC Radio 5 Live's Sportsweek that McGregor should know his place.
"In the beginning, I didn't look at Conor McGregor as a boxer, this guy has never been 12 rounds and he's in there with a professor of boxing," the Briton said.
"Floyd took him to school, he made him punch himself out and when he was tired he took him out. It's textbook boxing.
"It shows that boxing is a superior sport. In the ring, you can't beat a boxer, it's not as easy as everybody thought it would be, just because McGregor is a fighter. This is fighting where you can only use your hands."
Despite Lewis' criticisms, the money the fight attracted means another boxing outing for McGregor seems inevitable, possibly against Paulie Malignaggi who has denied claims he was put down by the Irishman in sparring.
Lewis, though, hopes McGregor's ring appearance will never be repeated.
"I didn't see the point of the whole thing," he added.
"A lot of people found it exciting, could Conor McGregor beat Floyd? It wasn't the case. It was a case of a textbook style brought to school, Conor McGregor got brought to school. He got schooled."
Asked if he had a message for McGregor, Lewis said: "Stay in your lane. Boxing is superior."
Carl Froch admitted he was on the edge of his seat but also believes Mayweather "outclassed" McGregor.
Four-time world super-middleweight champion Froch praised the UFC star's resilience but the 40-year-old was not surprised by the result.
Froch, speaking on Sky Sports Box Office, said: "He (McGregor) did well from the fact that he's a mixed martial artist. If that was a boxer, you'd say it was an 'outclassed' job, a mismatch.
"In reality, he (Mayweather) was in there with a UFC fighter. Conor came, he was proud, he tried, he didn't go over.
"It was a great event, promotion, a good show, we've all been on the edge of our seats. But what happened is what we thought would happen."
Boxing promoter Frank Warren was critical of the quality of the fight and he believes the Irishman was "totally out of his league" to stand in the ring with one of the greatest boxers of all-time.
"I've never seen him fight as a boxer but having watched that, he can't box. He's brave, he's got a big heart but he's not a boxer and like Lennox (Lewis) did say, he (Mayweather) took him to school," Warren said.
"He was just out of his depth. He won the first three rounds but Floyd barely threw a punch, he'd been out of the ring for two years, (and) 40 years of age. And by the way, I didn't think Floyd looked so good at times in the fight.
"But he (Mayweather) knew that he could walk through this guy, he knew after five rounds that McGregor had never been five rounds and that he could just wear him down.
"I'm confident that British (welterweight) champion Bradley Skeete could beat him. He's not a boxer. It just showed that he was totally out of his league.
"It was what it was, two cultures - UFC and boxing - those two cultures clash and the bottom line was that Conor McGregor should stick to UFC, that's the fact of life.
"It brought the whole world's attention to boxing and it seems people are pleased with what they have seen. The two guys have made a lot of money and good luck to them. And Conor McGregor has more money than probably most British boxers combined in their whole careers."
UFC fighter Danny Roberts does not believe there will now be a flood of mixed martial artists heading for the ring.
Asked whether this sets a precedent for UFC fighters to take on boxers in the future, he said: "I can understand it, but at the same time I feel this is a one-off, the best of the best from two combat sports.
"As much as people want to talk about it from the outside, I don't necessarily think it is going to happen again, it was a spectacle."