who should i have a a goal keeper

[X101]

What's the go on using goal keepers outside of goal when you have a high number of injured players, does it incur a possession penalty?

[Tactician]

What's the go on using goal keepers outside of goal when you have a high number of injured players, does it incur a possession penalty?

I can't confirm about the possession penalty, but almost sure the other team is going to beat you if he has more or less the same quality.
So, do not play a GK as an outfield player and surely do not play an outfield player in GK position. If you have a lot of injuries, get at least temporary players for the required positions from the transfer market. If you have little amount of money, look for the 'free' ones.