The on-loan midfielder has found himself on the outer in recent weeks, with BILD quoting a source stating: "He's very angry and does not understand the world anymore".
However, F95 coach Friedhelm Funkel insists: "Lewis will also get his chances again. He has offered more in practice during the last two weeks. He did not believe that before.
"I have an oversupply in midfield. We have a lot of important players there."
He added: "One has disgruntled players. I have never experienced a satisfied player sitting on the bench."