Bayer Leverkusen will be unable to field Turkish International Hakan Calhanoglu for the rest of the Bundesliga season after the player was slapped with a four-month ban for a breach of contract.
Calhanoglu, 22, must also pay Turkish club Trabzonspor a fine of 100,000 Euros (£85,900).
Trabzonspor had lodged a claim with FIFA in 2013 that Calhanoglu had agreed to sign for as a teenager from Karlsruhe in 2011, but the player had remained in Germany.
FIFA ruled in favour of Trabzonspor and after an appeal to the Court of Arbitration for Sport, the decision was upheld.
The CAS announced that the FIFA ban, which was frozen pending the appeal verdict, “is reinstated with immediate effect.”
Leverkusen sports director Rudi Voeller said the club “cannot comprehend” the decision, adding it was a “heavy blow for Hakan and us”.
“Although Bayer Leverkusen had nothing to do with this it is also punished,” Voller said. “Now we will miss an important player during a decisive part of the season.”
“We obviously regret this decision, which we cannot follow in any way.”
At the time of the approach from Trabzonspor, Calhanoglu was 17. He eventually left Karlsruhe to join Hamburg in 2013, before joining Leverkusen in 2014.
Calhanoglu, who has seven goals for Leverkusen this season, will miss Champions League matches against Atletico Madrid and will also suspended for Turkey’s World Cup qualifying match at home against Finland on March 24.