Without Mbappe, PSG neglected to penetrate an amazing protective exhibition from City and didn't enroll a shot on track, with substitution Mauro Icardi incapable.
"That [Mbappe's absence] can't be a pardon," added Pochettino, a Champions League finalist with Tottenham in 2019.
"We are a group. Obviously, it's unfortunate he was not prepared to help the group, yet that is not a pardon. We can't utilize that pardon on the grounds that the exhibition from the group was acceptable.
"We played the game we intended to play. We began truly well, making possibilities and overwhelming Manchester City. That is difficult.
"Here and there in football you need a level of karma in certain times of the game. They scored from a circumstance where we were squeezing high, with a long ball.
"The players will all vibe disillusioned. We progressed nicely. The arrangement, the game was acceptable. This kind of game you need karma to turn out well for you."
Pochettino glad for players' 'battle'
In the main leg, PSG had Idrissa Gueye shipped off and they likewise finished with 10 men at Etihad Stadium after Angel di Maria was shown a straight red card for kicking out at Fernandinho.
Pochettino, whose side are second in Ligue 1, one point behind pioneers Lille with three games to go, added: "With the red card of Di Maria, that changed the inclination.
"It was hard for the group and we were open. In any case, the group consistently battle - that is the reason I am glad for my players.
"That is the main thing. We were alive. Obviously I am baffled. I'm not going to mislead anybody and say we are positive."
After the match, PSG players Ander Herrera and Marco Verratti purportedly guaranteed official Bjorn Kuipers swore at them during the game.
Talking in his news gathering, Pochettino said: "They clarify in a meeting with the TV. I figure we should accept what they are advising us.
"Assuming there is something there and that is the manner by which they clarify, possibly Uefa will explore the circumstance."