Playing injured players

My keeper got carried off in the last match, the 2nd to last game of the season, with a cup final to follow. I'm pretty sure I'll be able to play him, but he'll still be slightly injured. I've never had an occasion before where I was prepared to risk it, as his replacement is only a reasonable keeper in comparison. I'm not that worried about him being out for longer it being the last game and all.

However, when you play slightly injured players, what happens? Do they play the game with the green cross over their head? Do they play worse than usual? Is it any different when its the keeper, since fitness doesn't really matter? In short in your experience is it worth it?

I've not been able to locate a thread on this topic elsewhere, but would be grateful if anyone has seen any others.

I only ever play players with slight injuries as emergency subs, I never start with them but keepers are different, if its an important game i'd risk it.

Played the injured keeper, it didn't make any noticeable difference, certainly didn't play badly. Did lose on penalties though.