This is a stupid question, so be forewarned. Why is it that a player rarely play full seasons? I know injury and suspension has a lot to do with it, but a red card is virtually the only way to get suspended in league play yet players rarely play all 38 or 34 or whatever matches. Is there some sort of lineup rotation tactic that managers use that I am unaware of. I know some managers rest star players in league matches before big contential matches, but is this consistent. What am I missing here? Besides common sense?