Once again - I don't know how advanced this game is. But I do play football manager nonstop. If you think about it, how likely is it that a manager puts in a player on the field a day or some day after hes back from an injurie? I myself suffer from injuries and it is as you all say here (usually the player that got back from injurie, gets injuried again.) So i simply let him rest from games 2-3 days and voila... his fine. Give the player 2-3 days to cover up... (once again - I don't know if the game is this advanced or not.)