Christian Heidel has announced he is stepping down from his role as Schalke's sporting director as the club remains mired in difficult 2018-19 campaign.
Heidel's contract was set to expire in 2020 but he will instead leave the Bundesliga club at the end of the season at the latest.
But results in the Bundesliga have been poor with the club 14th in the table after Saturday's 3-0 loss at Heidel's former club Mainz.
Heidel has been linked with a return to Mainz but said he will stay at Schalke until they are ready to appoint a successor.
"In the past three years, we have enjoyed success in achieving second place in the Bundesliga, reaching at least the quarter-finals of the DFB-Pokal and Europa League, as well as the last 16 of the Champions League," he said in a statement.
"In the Bundesliga this season, we are falling short of our expectations for a number of reasons. Even though a few things haven't gone our way this season, I certainly hold the responsibility.
"Additionally, the work I do with my colleagues with the executive and supervisory boards is based on nothing but mutual trust. With clear heads, we've been able to develop together in many areas, but this clarity can no longer be guaranteed, which first and foremost relates to discussions about my role.
"In my life, I've always been resolute. Therefore, I informed Clemens Tonnies, chairman of the supervisory board, of my decision last Monday. I hope that everyone in the club can now focus fully on the future."
Tonnies said he regrets Heidel opting to leave but indicated Schalke's search for a replacement will not be rushed.
"I am sorry that Christian Heidel has had to make this decision, one which he has certainly not taken lightly," he added. "We will continue to work together with full confidence and responsibility, of course.
"His decision has shocked us. We will carry out and present the succession process in due course. This will be done quickly, but it shall not be a rash decision. We thank Christian Heidel for the work he has done for Schalke."