The Premier League leaders eased towards the quarter-finals of the competition with a routine 2-0 win in the first leg of their last-16 tie against the German side in Budapest.
Bernardo Silva and Gabriel Jesus scored either side of half-time – both goals created by Joao Cancelo – while Monchengladbach offered little, but Guardiola was concerned about a lack of clear-cut chances.
“The second leg is in three weeks. The next target is West Ham. That is my only concern.”
Monchengladbach coach Marco Rose admitted it had been a tough night for his side.
He said: “We came up against a brutally good team that we had to fight against. In that type of form, they’re so hard to stop.
“Especially in the first half, we barely broke into the final third. We defended relatively well but it’s so hard when they keep throwing everything at you.
“We could have done things better and we will analyse the match. It would have been nice to score a goal to be in a better situation.”