Andreas Müller was initially loaned from Karlsruher SC to Fortuna Düsseldorf. The loan includes a purchase obligation that is activated if Fortuna Düsseldorf achieves promotion. According to BILD, upon promotion, Fortuna Düsseldorf would be required to pay 200,000 Euro to Karlsruher SC, and Müller's contract with Fortuna Düsseldorf is set to run until 30 June 2030. During the loan year, Karlsruher SC will continue to pay approximately 30 percent of Andreas Müller's monthly salary. The purchase is set to officially occur in the upcoming summer.

According to Bild, Andreas Müller, 26, completed a transfer from KSC to Fortuna after the Mannheim match for which no fee was paid.

According to Bild, Andreas Müller has joined Fortuna Düsseldorf, and manager Samir Arabi negotiated top conditions with Karlsruher SC for the transfer.

According to Bild, Fortuna Düsseldorf is interested in acquiring Andreas Müller from Karlsruher SC. Andreas Müller, 26, is Fortuna Düsseldorf's intended main number-6 midfielder, but his current club, Karlsruher SC, has not yet accepted the transfer conditions proposed by manager Samir Arabi. Fortuna has already signed Marcel Benger as a low-cost option, which also addresses the possibility of them failing to acquire their main target. It is reported that the club hopes the deal for Müller will be completed quickly. The German midfielder joined Karlsruher SC in July 2025 and has a market value of €800k, according to Transfermarkt.