Galatasaray have confirmed the resignation of Mustafa Denizli less than four months after taking over at the Turk Telekom Arena.
Denizli was appointed Hamza Hamzaoglu's replacement in November but Gala have struggled for consistency and bowed out of the Europa League following their Champions League group-stage exit.
The defending champions sit fifth in the Super Lig after Sunday's defeat to mid-table Gaziantepspor and Denizli was initially reported to have offered his resignation on Monday.
The club confirmed his departure a day later, with Denizli replaced by coach Orhan Atik.
"We must create the future rather than save the day," read a Galatasaray statement.
"On the other hand, we cannot neglect today where building for the future is concerned. In this transition period, all wearing the Galatasaray shirt must have, in their natural duty of professionalism, a greater sense of responsibility."
Atik's first task in charge will be the second leg of Gala's Turkish Cup quarter-final against Akhisar Belediyespor, with the Istanbul club leading the tie 2-1 ahead of Wednesday's clash.