Pedji explanation is simple enough; he was not referring to injuries but only to illness. As in Barton's case it is when the Club fails to give clarification on a Players absence do 'misunderstandings' occur; so if player Taylor is injured then it is the Clubs responsibility to say so ....and quickly. If a player is ill then the Club needs to handle the situation differently and crucially in consultation with the Player.
"Not fit" covers every thing doesn't it ?