The Player's Guide says Durability (du): refers to how a player deals with injuries - the higher a player's durability, the less likely they are to sustain a severe injury and when they do get injured, how quickly they'll be able to return.
But, does the rating also work with STAM during the course of a game? After the player is tired, does durability effect how quickly he recovers STAM and how quickly he tires again after already been worn down or do the two ratings stand alone.