Mayweather came out of retirement to fight the Irishman on 26 August as the former five-weight champion comfortably came out on top, stopping McGregor in the 10th round.
The win gave "Money" his 50th professional win as he overtook Rocky Marciano's record of 49-0, with many claiming the accomplishment cements him as the greatest boxer of all time.
Sanchez, however, disagrees, claiming that a win over a mixed martial artist does nothing for Mayweather's legacy.
"As important as it is for him to be 'TBE' and as important as it is for him to be recognized as one of the best, I'm surprised that he made this fight," Sanchez said, as quoted on BoxingScene.
"I understand the financial part of it for him, but it does nothing for his legacy and I think for us to consider that being one of the 50 fights would be bad for his legacy and to his image."
Sanchez went further and compared the McGregor to win a baseball player using performance enhancing drugs before adding that Mayweather would have to fight at least once more for his legacy to remain intact.
"If he retires and does nothing after that, I don't think that it will be something that will be considered as breaking the record of Marciano," he added. "It's just like when these baseball players were caught using performance enhancing drugs, how can you put those records on file and consider them with the records of the guys that didn't?"
"I think of this talk about an asterisk besides their name for this being done while using the performance enhancing drug. For Mayweather fighting an amateur, it shouldn't be considered as his 50th win. What he does after this fight will determine how he's viewed at the end of his career."
Meanwhile, Golovkin's promoter Tom Loeffler recently claimed that Mayweather only took the McGregor fight because he was scared of facing "GGG".