Coutinho missed the first five matches of Liverpool's season, but was able to make two substitute appearances for Brazil over the worldwide break.
The German coach will guide his side back to Champions League action for the first time since the 2014/15 season - where they crashed out in the group stages in disappointing fashion.
"He has been at the club nearly two years".
He said: "Leaving Coutinho out against City was a decision made with the season in mind".
'If they train bad they don't deserve a game, but they both train really well.
PSG to be without Angel Di Maria and Javier Pastore at Celtic
Neymar , Mbappe and Cavani (twice) all scored - and Celtic back Mikael Lustig contributed an own goal to complete the misery. In the first half-hour of the second half, we were much better but you can always concede against players of that quality.
"That's the plan. Not to keep them happy, no, to use the quality of the goalkeepers and that's how it is, to keep them altogether and then they will decide with the performance who will play".
"We play on Wednesday, we play on Saturday, we play, play, play, play, play".
The Merseysiders return to Europe's elite competition when they welcome Sevilla to Anfield on Wednesday night but it looks like they could be without one of their key men. Mo we sent him home tonight.
However, Liverpool could be without Mohamed Salah, who missed training on Tuesday due to illness.
The attacker has chipped in with three goals in his opening six matches for the Reds and he was rewarded with the Liverpool Player of the Month for August so I'm sure Klopp will be desperate to have him available for selection tomorrow.