I have never bet against Mayweather, but (depending on the odds), this might be the one.

Mayweather is 44-0-0

"Canelo" Alvarez is 42-0-1

Mayweather just signed a big contract with Showtime (basically five fights). Assuming he wins the next five fights (including this one), he will be at 49-0-0. That would tie him with the record of the great Rocky Marciano (49-0-0). I would think he would do one more big payday fight after that to have the "undefeated champion" record. I think his ego is too big to just tie that record.

I have read a bunch of articles that have said Canelo is getting better with every fight and that Mayweather wanted to fight him ASAP before he gets any better. If Mayweather wins the fight with Canelo, it is most likely that Canelo will never get another shot at him. However, if Canelo wins it, Mayweather would probably want a rematch - a huge payday for both. Canelo has everything to gain, and nothing to lose. Add that with the fact that it appears Mayweather is looking beyond the fight to his 50-0-0 retirement, I smell $$ to be made.