Borussia Dortmund coach Thomas Tuchel has said winger Ousmane Dembele is walking "a fine line" after he picked up his fifth yellow card of the season against Hertha Berlin.
Dembele, 19, was involved in an incident with Hertha midfielder Mitch Weiser in the defeat at the Olympiastadion, and the France international will now miss Dortmund's match against Ingolstadt on Friday.
Speaking at his prematch news conference ahead of BVB's DFB Pokal trip to Lotte, Tuchel said that the youngster needed to mature.
"We are delighted about the bite he can develop in his game, but it's a fine line that he feels treated unjustly and says thing to the referee or makes comments resulting in a yellow card," Tuchel said.
He added that players "like Pierre-Emerick Aubameyang and Marco Reus" could help because "they are the players he looks up to and has the most trust in."
Dortmund are aiming to reach the semifinals of the DFB Pokal, where Bayern Munich would await.
They will be without the suspended Sokratis Papastathopoulos and the injured Julian Weigl for a match that was rescheduled after a snowstorm at Lotte two weeks ago.
Tuchel said: "It will be a very tough task. We will give it everything we've got to reach the next round."