A 1-1 draw in Istanbul on Wednesday has put the Royal Blues in a good position to reach the quarter-finals of Europe's premier club competition.
Their position in the Bundesliga is not so promising, however, and fixing that is their current priority.
"We really have to build on this," captain Benedikt Howedes said on his club's website. "Dusseldorf certainly aren't going to be a walk in the park for us, but it has got to be our aim to beat them.
"I am convinced that we will be able to latch onto our good performances from the first half of the season and make up some ground in the table."
To do that, coach Jens Keller has to motivate his team again for what is arguably a less attractive game, and one which may be a touch easier to underestimate.
"We can expect a game against Dusseldorf in which we are going to have to be patient," he said. "That is why we are probably going to have to need a bit more passion."
Fortuna will be making their first ever visit to the Arena AufSchalke on Saturday.
The last time the two sides met 16 years ago, the Royal Blues were still playing in the nearby Parkstadion and Fortuna came away with a 1-0 win, extending an unbeaten record in Gelsenkirchen which dates back 26 years.
Extending that record will be coach Norbert Meier's priority on Saturday as Fortuna look to at least maintain an 11-point cushion over the relegation zone, while a win would take them above their hosts in the table.