Crawford, who's ranked third by both ESPN and The Ring, praised Mayweather's skills and record. He said:
"In my opinion, the best boxer in history is Floyd Mayweather. His punching was very powerful. Floyd defeated almost all of his opponents during his professional career."
Mayweather's career stretched from 1996 to 2017. He retired with a perfect 50-0 record, beating big names like Manny Pacquiao, Canelo Alvarez, and Oscar De La Hoya. Fans and experts often point to Mayweather's great defense and top-notch technique as reasons for his success.
Crawford, who's 37 and from Nebraska, currently holds the WBA super welterweight title. He'll move up a couple of weight classes to face Canelo in their upcoming fight.
Not everyone agrees with Crawford's pick, though. Canelo himself has a different opinion on who's the greatest. He's said:
"The greatest of all time is Muhammad Ali."
Mike Tyson backs up Canelo's choice. Tyson once said:
"Nobody can beat Ali, I can't beat that guy, no way. Impossible."
These different views show how tough it is to pick just one greatest boxer. Other names that often come up in these talks include Rocky Marciano, Joe Lewis, and Manny Pacquiao.
As for Crawford, he'll try to add to his own great career when he steps into the ring with Canelo in September. It's a big jump in weight for Crawford, but a win could put him in the conversation with some of boxing's all-time greats.