City will be hoping to take a step closer to the knockout stages of the European competition as they host the Belgian champions at the Etihad Stadium.
The Premier League side ran out 5-1 winners when the sides met a fortnight ago but Guardiola is not taking anything for granted ahead of the return.
Guardiola said: “I think this game is much more important than the United game.
“This gives us an incredible chance to qualify for the last 16 of the Champions League. In the Premier League there are many games, in the Champions League just six, and there are not many left.
“Games three and four are the most important. I’m pretty sure they will adjust things to punish us. We have to adjust to get better. It will be a completely different game.”
City were surprisingly beaten at home to Crystal Palace last weekend but Guardiola remains happy with the way his team has been performing in recent weeks.
He said: “I think we have been playing at an incredible level in the last month, month-and-a-half, one of the best moments since we’ve been here.”