Arsenal boss Arsene Wenger feels William Gallas is still recovering from being stripped of the club captaincy last month.
Wenger told France Football: "On the human level, what happened with William was the most difficult thing I have had to handle in my career because I have a lot of esteem for him.
"He was caught in a media storm, a witchhunt that isolated him to the point where it became a handicap for the team. He has refound the stability in his game but I am not convinced that, in his mind, he has refound his stability and his joie de vivre."