You're never going to get evidence are you - it's not like a former Forest player was caught playing football with his mates, when the manager at the time said he was injured - only for him to move not long after.
Managers often state that a player is injured - it's easier than saying he's not playing because he's agitating for either a new contract or a move.
Holmes did not play for Derby from mid December, he wasn't injured & his comments in that article are a damning indictment of how they work.
I can't give you evidence that Tiago Silva was injured, but he wanted the move & refused to play - easier for Sabri etc to just say he was injured.
Of course we have plenty of genuine injuries, but it's so easy for a player to say - 'sorry, can't train today - rolled my ankle walking the dog, felt my hamstring twinge, picking up my wallet........'
Magically, Samba Sow has probably managed his longest run of games.... what is the motivation? - shop window, new contract.