City have won 10 of their opening 11 games, and only a home draw against Everton in August deprived them of a ideal start.
"They are a good side but they are not an unstoppable side", Wenger said.
Sterling went down in the area under pressure from Nacho Monreal just after half-time in their final match before the worldwide break, and Sergio Aguero duly converted the penalty.
Wenger also criticised referee Michael Oliver and called Raheem Sterling a diver for a second time after the defeat to City.
"People always want to predict what will happen", he added.
"The referee had an absolutely atrocious input".
"I don't think that will be possible because I think you have so many games and too many important games", De Bruyne told Sky Sports News. We conceded a penalty that was not a penalty and an offside goal. It was not to blame Raheem Sterling - he used his advantage to fool the referee, that's what he did.
Wenger also suggested the clash was closer than the result suggested, citing "expected goals" statistics.
Last month's defeat has left Arsenal sat in sixth in the Premier League, 12 points off Pep Guardiola's side.
Results also got off to a shaky start, notably the 4-0 hammering by Liverpool at Anfield, but they've lost just once in 14 games since then.