Bayer Leverkusen have confirmed their midfielder Hakan Calhanoglu is involved in a legal dispute with FIFA that relates to a contract he signed with Trabzonspor in 2011.
The Bundesliga club expects the proceedings to last for "several months", during which time Calhanoglu will remain eligible to play.
The 22-year-old German-born Turkey international came through the ranks at Karlsruher, who he represented between 2009 and 2013 – albeit on-loan from Hamburg during the 2012-13 season.
As a 17-year-old, Calhanoglu signed a deal with Trabzonspor to join them for 2012-13 but the move collapsed.
He joined Leverkusen from Hamburg on a five-year deal in 2014 and his current employers issued a statement to clarify that the dispute does not relate to this transfer.
"FIFA and Bayer 04 Leverkusen player Hakan Calhanoglu are currently involved in a legal dispute," the statement read.
"The case relates to a contract with the Turkish first division club Trabzonspor who Calhanoglu signed for as a minor at the age of 17. The agreement envisaged the midfielder playing for Trabzonspor from the 2012-2013 campaign.
"The move did not take place at the time primarily due to the lack of agreement between Hakan's former club Karlsruher SC and Trabzonspor.
"The case is expected to last for several months. Hakan Calhanoglu remains entitled to continue playing football."
Calhanoglu has scored eight goals in 39 matches this season for Leverkusen, who will aim to turn around a 2-0 deficit in the home leg of their Europa League last -16 clash against Villarreal on Thursday.
