Defeat at home to West Ham last Saturday saw the Bluebirds slip into the Premier League relegation zone, and their next outing is the daunting prospect of a visit to the Etihad Stadium, where City are unbeaten in the league this term.
Manuel Pellegrini's side have scored 38 times at home in the league this season, and they thrashed West Ham 6-0 in the Capital One Cup last week, but Marshall feels his side can draw confidence from their 3-2 win over City at home in August.
"Manchester City away is a huge challenge, but it's one of those games that you look at and there is no pressure on us," said Marshall.
"If we turn up and get done like almost every other team has there this season then no one is going to bat an eyelid. There was no pressure when we beat them at home at the start of the season.
"Obviously they have been flying and scoring so many goals. They've won so many at home so it's going to be difficult.
"The first goal proved vital against West Ham so we are going to have to try to get the first goal against Manchester City. We are going to have to stick together and start well. If you concede early on at a place like that then you are facing a massive uphill battle.
"Crystal Palace did well there though recently and were a bit unlucky so we'll go there with confidence. We'll try to get points. We've dropped into the bottom three and we do not want to get cut adrift in there. So we are going to have to put a strong performance in.
"But we've beaten them at home so maybe the double is on."