The France attacker's future is again up for discussion, with more discipline problems being raised.
Stephan worked with Dembele at Rennes and told Le Parisian: "At home, he was never injured. He worked all the sessions and all the matches without a physical glitch.
"He was always the first to train, he loved it. I do not know what is happening today in his daily life but, inevitably, he struggles. There are reasons for all this, that's for sure.
"He must understand them and rectify things so that it does not happen to him anymore."