Wawrinka wasnt tough opponent for Federer.
But if he was in Fed's side of a draw , and if he delivered same kind of A game which he did against Djokovic I am sure Federer would loose that match.
Simply because Djokovic is better defender and grinder than Federer is.
Also Djokovic has bigger balls and mental strength .
Federer has better serve and forehand.
But Djokovic is able to nullify his serve and FH with his ROS and great defense.