The German has spent most of his career as a deeper lying midfielder, but started playing further forward last season for City.
Gundogan, who often popped up with vital goals last season, may have to play a similar role this term as City failed to sign a centre-forward in the summer transfer window.
Asked about Gundogan before a Champions League group stage clash with Club Brugge on Wednesday, Guardiola told reporters: "Every player is so important. You have to understand there are injuries and highs and lows in careers.
"What a player did lasts season doesn't mean he will do it again.
"Ilkay is so important, you know, he is intelligent, always thinking what is best for the team, but he was injured and needs time.
"He is getting better and we need him like we need all the players. He will; be much better in a few months and there are others who need to play now because they are in top form and may drop later.
"You have [to] maintain it every day. That's why these players get credit for the last 6 years because it's every day. Tomorrow we have a chance.
"The group stage every year is more tricky. We already lost and now the games at home we have to take it.
"Tomorrow we have an incredible opportunity to step forward."
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