Schalke boss Ralf Rangnick has been told he will not be able to spend all of the money generated by the sale of Manuel Neuer to Bayern Munich.
Germany international Neuer moved to the Allianz Arena for a fee reported to be in the region of 20 million euros last month.
Rangnick had hoped to reinvest it in the squad, but talks over the weekend with sporting director Horst Heldt and chairman Clemens Tonnies revealed some of the income would be used to satisfy the club's existing debt.
A disappointed Rangnick said: "I assumed that we could invest the money from the sale of Manuel Neuer and put it back in the team. That would be normal, but it is not the case.''
Rangnick would like to bring in a striker with Freiburg's Papiss Demba Cisse and Brest's Nolan Roux at the top of his list of targets.
But Heldt admitted the club was taking a cautious approach in the transfer market this summer. He said: "We are continuing our policy of providing money to make us competitive but we also have to think about consolidating the future of the club.''