Thomas Tuchel was unimpressed by Kylian Mbappe's reaction to being substituted in Paris Saint-Germain's 5-0 win over Montpellier on Saturday.
Mbappe scored PSG's fourth goal at Parc des Princes, having earlier hit the post as well as playing a part in the sending off for Montpellier goalkeeper Dimitry Bertaud.
With PSG five goals up with 68 minutes gone, Tuchel opted to withdraw the 21-year-old, with Mauro Icardi coming on to replace him.
But Mbappe was visibly annoyed with the decision, vocally questioning head coach Tuchel, who continued his attempts to respond to the forward before he sat down in a heated exchange.
The France international did take his place on the bench but continued to look disgruntled.
"I'm the coach, someone has to decide who goes off and who comes on – it's me," Tuchel said during his post-match news conference.
"He is very intelligent, he knows what he is doing. He doesn't like going off, nobody likes going off.
"These are not good images, but we are not the only club that has to deal with this sort of thing. It's not good, because it opens up subjects that go against the team's state of mind. Too bad.
"I am not angry, but I am sad because it is not necessary. I explained to him why we did this, and it will stay that way. I will always decide the technical aspects. We don't play tennis, we play soccer and we have to respect everyone."
Tuchel was asked what the next steps would be and refused to rule out punishing Mbappe.
The former Borussia Dortmund boss added: "I don't know, I have to think, I have to sleep.
"I will make a decision. We have training at 11am, we will talk about the match with the group. I'll see if I talk about this or if I do it individually. It will depend on my night's sleep too!"
PSG enjoyed a comfortable afternoon in a match that was all but over after 17 minutes, Pablo Sarabia scoring before Bertaud, who handled outside the area while attempting to stop an Mbappe shot, saw red.
Angel Di Maria's strike and a Daniel Congre own goal had PSG three up at the break, with Mbappe and Lavyin Kurzawa on target after the break.
Montpellier ultimately finished with nine men after Joris Chotard received a second booking two minutes from time.