Luis Enrique took off France captain Mbappe in the 65th minute with PSG losing. His replacement, Goncalo Ramos, won and converted an added-time penalty that gave the home team a 1-1 draw in Ligue 1.
Mbappe has said he plans to leave when his contract expires after this season with Real Madrid expected to be his next destination.
"It's very simple, sooner or later, when it happens, we have to get used to playing without Kylian," Luis Enrique told the post-match press conference.
"When I want him to play, I'll play him, and when I don't, same thing."
Between the 64th and 70th minutes, Luis Enrique replaced his entire forward line, also taking off Ousmane Dembele and Bradley Barcola.
"It's a message for everyone," said Luis Enrique immediately after the game. "If you think I'm going to accept a player slacking off on the pitch, I'm not."
At the press conference he stressed that he was not singling out any players and that the whole team was "less inspired" than usual.
"No, no, you've got it all wrong. It's a message for everyone. I'm delighted with the attitude of my players. But if anyone thinks I'm going to give up on them, I won't.
"I wanted to change the feel of the match. I didn't want to take off Dembele but I thought he was hurting.
"I'm lucky enough to coach around 20 very high-level players, and I want them to understand that every minute has to be earned."
"I want maximum competitiveness. I want every player to deserve his playing time," he said.
"I want my players to say to themselves: 'When I'm in the starting line-up, I have to make the most of it'."
PSG, who have an 11-point lead over Brest in Ligue 1, face third-placed Monaco on Friday before travelling to San Sebastian to face Real Sociedad in a Champions League round-of-16 second-leg game on March 5th, holding a 2-0 lead from the first leg.
"I'm loving it," said Luis Enrique. "I'd like every match to be like that, like Brest, Monaco and Real Sociedad. The tougher the games, the better. Does anyone think the return leg will be easy against Real Sociedad?"
