Last year's Turkish champions Galatasaray coach Mustafa Denizli is due to resign on Monday, after a three-month spell with the club, a source close to the matter told Reuters on Monday.
Denizli took charge at the club in November after former coach Hamza Hamzaoglu stayed less than a year at the helm.
The Istanbul Lions have struggled this season, ranked fifth in the domestic league and fourteen points behind leaders Besiktas. They were also knocked out of the Europa League last week.
The club had no comment on the report.
Denizli did not coach the team at a training session earlier on Monday.
Denizli, 66, managed the Turkish national team for four years and reached the quarter-finals of Euro 2000. He won three domestic league titles with Istanbul's three arch-rivals -- Galatasaray, Fenerbahce and Besiktas.
Galatasaray may face a ban from Europe's ruling body UEFA later this week over its failure in following the financial fair play regulations.
UEFA said last month the Lions had failed to comply with its rules governing the permitted level of financial losses, paving the way for a potential ban from European competition from UEFA's Club Financial Control Body (CFCB).