Schalke have warned former Spurs midfielder Nabil Bentaleb that he must change his attitude, sporting executive Christian Heidel told reporters on Thursday.
Bentaleb joined Schalke on loan in 2016 and made the move permanent for a reported €19 million last year.
But after making 32 Bundesliga appearances in his debut season, his second has been marred by injuries and a conflict with head coach Domenico Tedesco as he has played only seven times in the league.
Tedesco told a news conference: "It's common knowledge that we've not been happy with Nabil's manner in recent weeks.
"We have now got the squad on board, and have addressed it. It's up to him now, and in a one-to-one everything's good."
Heidel backed his coach and said "team interest is always above individual interest."
He added: "He's not a bad person, but he's over-ambitious. Everything's bad when he's not playing.
"We could win 5-0, but if he were only to feature for 45 minutes he'd make a face as if we had lost 5-0."
"If all of us were to think that way, we'd have a problem. Thank God that's not the case. Nabil must change, and he understands it."