Difference between picking up a knock and just being injured

So far in the game I have run across three types of injuries in-game:

1) Player is injured and needs to be removed from the game

2) Player needs physio treatment but returns to play, often after sitting out on the side lines for a while. Player condition is reduced to varying degrees and seems to slowly creep up in the positive direction as the game goes on.

3) Player picks up a knock and has a green box with a white cross icon above his head. He remains in the game and his condition has been reduced. I have seen some players condition improve, others not.

So my question is, what is the difference between items 2 and 3? Or more precisely what I'd like to know is how to judge the ability of the player to continue in the game and contribute.

What I'm hoping is that I can just look at the condition and base my decisions off of that alone. So a player with a 70% condition is better off than one with 69% condition, etc.

But I'm wondering if, instead, something like this in in place: a player with a knock and 70% condition is worse than a player who was injured without a knock and has 70% condition.

If someone could explain the nuances between injured with a knock versus injured without a knock, I'd be appreciative.

If a player gets a knock I sub him off immediately, if he stays on I find it increases the chance of full injury

2) Isn't an issue at all, reduces condition but doesn't result in an injury.

3) Green cross is a potential injury, leaving him on increases the risk of making the injury worse but you can normally tell by watching his condition. If it goes down fast I tend to take him off but if he more or less recovers the injury will just hamper him for the rest of the match and I'll leave him on a bit longer. Either way unless I have problems I would tend to take him off at some point later on. He may or may not have an injury after the match.

When a player has a green cross icon, you can also click onto his profile and where it says 'condition' it tells you if he has an injury or not. e.g. 'has a potential foot injury'.

If they do the green cross it doesn't always 100% of the time say they've got an injury though, in which case you could leave them on if their condition is high enough and I'm guessing it won't affect performance.

That's just my personal experience though. Hope it helps.

If you have the motivation widget on when you play in 3d then it will give you some detail. So and so is injured but they feel they can shake it off is one of them. Never seen anyone lose the green tag though.