How much soccer is too much in a given week?

I understand that's this depends completely on the level played. But at the higher levels is there an optimal number of practices/games that should be played in a week. I would think there's a fine line between between just enough and too much. I am thinking three times a week when playing games on the weekend. If not playing games, maybe add a practtice. I have seen players who either practice or play games nearly every day of the week. They also seem more prone to injury. With the demands of this sport I would think there needs to some recovery time in the mix to keep these kids healthy. I recognize that guarantees nothing, but I'm just wondering your thoughts.