Loris Karius is reportedly prepared to take Besiktas to court after going four months without being paid by the Turkish club.
The 25-year-old joined the Super Lig giants from Liverpool last summer on a two-year loan deal that has the option to be made permanent.
Karius has not had an easy time of it since making the switch to Vodafone Park, however, having been criticised by manager Senol Gunes last week for his recent performance.
Gunes told reporters: "Karius has gone a bit stagnant, something is wrong with his electricity, motivation, enthusiasm for the game. It has been like that since the beginning. He does not really feel a part of the team.
"It's something we haven't been able to work out and, of course, I am partly to blame for this. Something is wrong, he has also been unlucky. He is talented but it hasn't worked out and we have a problem."
German outlet Bild claims that the goalkeeper's problems are mounting, meanwhile, as he has not received any wages since the back end of last year.
The report suggests that Karius is owed around £1m and has lodged a formal complaint to FIFA, and he is now ready to take legal action to resolve the matter.
