Laurent Blanc says he understands Edinson Cavani's frustration at being substituted on Saturday, but also had a warning for the striker.
Cavani scored the opening goal in Paris Saint-Germain's 4-1 victory over Troyes - a superb cushioned volley from Angel di Maria's chipped pass.
Zlatan Ibrahimovic, Layvin Kurzawa and Jean-Kevin Augustin also netted, but Cavani was less than impressed at being replaced 10 minutes from time and appeared to mutter something towards Blanc as he walked off.
"Cavani wasn't very happy, I can confirm that," said Blanc afterwards. "But they are never happy and I can understand that.
"If established players have no motivation, we will play young people. They will be happy to play, but I think the established players that I have are currently serious."
Victory means leaders PSG have now won nine in a row in the league and are guaranteed to head into the mid-season break top of the table.
France defender Kurzawa called it a "beautiful evening" as PSG played at home for the first time since the November 13 terror attacks on their city.
The match was preceded by a series of tributes to the victims of the attacks which killed 130 people in the capital, with a huge French flag on the pitch and another formed by cards distributed to spectators.
The club anthem O Ville Lumiere and the French national anthem were both played before a pre-match minute's silence and a video tribute from famous faces from the world of sport.
PSG's players again bore the slogan 'Je Suis Paris' on their shirts on what was an emotional evening.
"It's a beautiful evening for us and for our fans," Kurzawa told L'Equipe. "I hope it will continue like that. You want to not lose and try to win every game to come.
"But we also know that it will be complicated. It [being autumn champions] means nothing. For me, what counts is to be champion of France in late season."
