Nt-Players don't seem to get injured. They're supposed to, but it's yet to be seen where a NT-player is injured in a NT match and the injury lasted longer than the game it happened in.
The quality of a doctor determines the severity of an injury, including converting some to injuries that only last the length of the game.
A level 10 doctor will convert over half of injuries to game-only. Maybe the NT have really good doctors.