I only carry the 1 keeper.

At level 31 I have never seen a keeper get sent off or injured in a game. I've seen them get injured through training, but never in an actual game.

I play a few friendlies each day too, but often either give my keeper an extra green pack to keep him going, or I throw an outfield player in goal. Interestingly I have not seen a massive decrease in quality when I've had an outfield player in goal.

In fact, in the past when I've used all my 3 subs and I get an injury in the game I ALWAYS swap my injured player with my Goalkeeper, so my Goalkeeper plays the rest of the game as an outfield player, whilst the injured player plays in goal and I have never suffered from the opposition smashing loads past me. It seems to be a bit of a trick you can exploit (A bit like setting your keeper to take pens/free kicks as you don't concede from doing that either) to get an extra outfield body on the pitch if you have used all your subs and get an injury.