The 22-year-old Turkey international must also pay €100,000 in compensation to Turkish club Trabzonspor, for whom he agreed to sign as a teenager, the Court of Arbitration for Sport ruled on Thursday.

Calhanoglu was a youth player at Karlsruher when he was paid €100,000 after agreeing to sign for Trabzonspor in the future. But he never joined the club, instead extending his deal with Karlsruher.

CAS said the FIFA ban, which was frozen pending the appeal verdict, "is reinstated with immediate effect."

Calhanoglu will miss Leverkusen's Champions League matches against Atletico Madrid and the rest of the Bundesliga season. He is also suspended for Turkey's World Cup qualifying match at home against Finland on March 24.

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"It's a heavy blow for Hakan, but also for us," Leverkusen sporting director Rudi Voller said in a statement. "Although Bayer Leverkusen had nothing to do with the events in 2011, we are now being heavily punished. Now we're missing a very important player during a decisive part of the season."

Leverkusen were not involved in Calhanoglu's breach, which came when he extended his contract with Karlsruher in 2011.

"We obviously regret this decision, which we cannot follow in any way," Voller said.

The Turkish club lodged their complaint with FIFA in April 2013. Calhanoglu has also played for Hamburg since he left Karlsruher.

Both Calhanoglu and Trabzonspor challenged FIFA's judgment in the case, and CAS said the club's appeal was only partially upheld.

"The club sought the return of a €100,000 advance that it had made to the player as well as compensation of €1 million," the court said.