BERLIN, Jan 13 (Reuters) - Schalke 04 general manager Rudi Assauer will be replaced at the end of the season and Andreas Mueller will take over responsibility for all sporting issues, the club said on Friday.Assauer had been criticised for his treatment of Ralf Rangnick, who was fired just before the winter break even though he led Schalke into the Champions League and was one of the most successful coaches in the club's history. Assauer will become president of the club, Schalke announced after a supervisory board meeting. 'We wanted to make concrete steps on the change in duties at an early moment to prevent any further speculation,' supervisory board chairman Clemens Toennies said. 'We agreed quickly in a very harmonious atmosphere.' Assauer, one of the Bundesliga's most colourful managers and famous for smoking cigars, has clashed with Toennies in recent weeks. Mueller has been Assauer's assistant for the last few years. 'I'm not going to let anyone drive me out,' Assauer said recently. 'My contract runs to 2008 and if anyone wants to change that, they're going to have to talk to me about it first.' Schalke are fourth in the Bundesliga, 13 points behind leaders Bayern Munich at the winter break.