It wasn't as bad since Floyd was coming off a two year retirement and Marquez was a pound for pound fighter, Khan on the other hand isn't anywhere near a pound for pound list, plus he's known for being chinny got KOd by Garcia in four rounds and always gets rocked by guys even Julio Diaz almost knocked him out, Marquez never was KOd.
If Khan was the best welterweight on the planet it would be ok but he's not, he's not even the third best welterweight probably not even the 5th best welterweight (Pacquiao, Bradley, Garcia obviously better, Thurman would KO Khan imo, Brook would probably KO Khan as well, maybe Khan could beat Porter though).