Huub Stevens has been sacked as coach of Schalke following their 3-1 defeat to Freiburg on Saturday.
Stevens was relieved of his duties after leading the club to just two points from their last six matches, although they have qualified for the last 16 of the Champions League as group winners.
Schalke's loss versus Freiburg leaves the club outside the top six of the Bundesliga going into the winter break, with youth team coach Jens Keller placed in charge for Tuesday's DFB-Pokal tie with Mainz.
"I can understand the question coming, but right now after this defeat at home, I have got to gather my thoughts and think of how we can approach Tuesday's game so that we can go through," said the club's director of sport Horst Heldt on Saturday.
"All other questions will be answered when the time comes."
A statement on the club's website says that the decisions "was anything but easy for those involved."
Information from the Press Association was used in this report.