Serbia's Viktor Troicki has appealed to the Court of Arbitration for Sport (CAS) over his 18-month suspension for violating doping regulations, the Lausanne-based tribunal said on Tuesday.
"The CAS procedure is in progress and a decision will be issued in around four months," CAS said in a statement.
The 27-year-old was suspended by the International Tennis Federation (ITF) in July for not providing a blood sample at the Monte Carlo Masters in April.
Troicki, a member of the Serbia team which won the Davis Cup in 2010, was ranked 53rd when the ITF announced his ban.
He is one of the most high-profile players to break doping rules in tennis
Troicki has denied any wrongdoing and said because he was not feeling well the doping officer had told him he could skip the blood test. Troicki had already given a urine sample.
He has been publicly supported by compatriot and world number one Novak Djokovic.
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