Oh, but I'm not saying Rio or Man Utd aren't hard done by how everything happened. If I'm not mistaking, he even voluntered to do the test just a few hours later, no? There could have been a bit more leniency from the FA in the whole situation. Although if you'd compare to how athletes are treated in some other sports, such as cycling, it's much worse there than in football.
But I was just talking about the punishment itself here, because I often see people compare this case with some other cases where the person has effectively been found positive for drugs. But if that is, let's say, cannabis or even cocaine, I think it's logical that the punishment is less severe.
Concerning the time to clear out drugs/doping, I thought so too at first. But apparently there are performance enhancing drugs that do clear out very rapidly and can become undetectable within 24 hours. But I'd have to look that up again to be sure.