The Bundesliga outfit are missing some key stars for their Champions League encounter and know a point would put them in a strong position in Group E
The Bundesliga outfit are missing key first-team stars Jefferson Farfan and Klass-Jan Huntelaar, who is out for the rest of the calendar year.
Schalke lead the group on six points, with Chelsea second on three, and Keller says he would be satisfied with a point at the Veltins Arena.
"Chelsea are a top side with enormous quality. We have a lot of confidence from our recent results as well as our good showings in the Champions League over the past years.
"With the fans in our back, obviously we want to give our best.
"I have always said I want to win every game. But you have to see how the game goes, maybe a draw would be ok and we could live with that situation."
Midfielder Marco Hoger tore his cruciate ligament on Saturday in the 3-2 win against Eintracht Braunschweig, but there was positive news on the injury front for Schalke.
"We are terribly sorry about the bad injury to Marco Hoger, but Jermaine Jones, Kevin-Prince Boateng and Timo Hildebrand will be back," said the coach.
"Boateng has trained a lot and will do so today. If he comes up to me and tells me he is fit, I will play him and we wish for that to happen.
"Lots of our current injuries came from accidents and cannot be put down to training problems. It is not so much bad luck, we just have to accept the situation and make the best out of it."