Pierre-Emerick Aubameyang was "stupid" for celebrating his goal against Schalke last weekend by donning a Nike mask, says Borussia Dortmund captain Marcel Schmelzer.
The prolific Gabon striker opened the scoring in the Revierderby, which finished 1-1, but his celebration angered Dortmund's kit sponsor Puma.
CEO Hans-Joachim Watzke vowed to hold a "difficult" conversation with Aubameyang over the incident and Schmelzer also warned his team-mate about his responsibilities.
"We already thought he would come up with something for the derby," Schmelzer told Sky.
"But what he did was stupid. None of the players knew that was coming.
"We have already had a word with him, the club will also have another chat with him and resolve the situation internally. Auba knows what the deal is.
"We know what he can do for us and he knows what we can do for him. The important thing is that we keep acting as a team. Auba is well aware of this and that is the most important thing."
The controversy did not prove to be a distraction for Aubameyang, who scored in Tuesday's 3-0 win over Hamburg to take his tally to 25 goals in an as many Bundesliga games this season.