Serbian tennis player Viktor Troicki has been banned for 18 months for a violation of the Tennis Anti-Doping Programme, the International Tennis Federation has announced.
Troicki, 27, failed to provide a blood sample when requested during in-competition testing at the Monte Carlo Masters on 15 April.
Troicki claimed he had asked permission to be excused the blood test due to feeling unwell, but that explanation was rejected by the governing body.
His suspension begins immediately and will end on January 24, 2015. Troicki must also forfeit all prize money and rankings points earned at the Monte Carlo Masters.
An ITF statement read: "Viktor Troicki has been found to have committed an Anti-Doping Rule Violation under Article 2.3 of the Tennis Anti-Doping Programme (refusing or failing without compelling justification to submit to sample collection).
"Mr Troicki, a 27-year-old player from Serbia, was notified on 15 April 2013 that he had been selected to provide a urine sample and a blood sample in association with his participation at the Rolex Monte Carlo Masters event.
"Mr Troicki provided a urine sample, but did not provide a blood sample.
"He asserted to an independent tribunal that he was assured by the Doping Control Officer (DCO) that it would be acceptable not to provide a sample on account of him feeling unwell that day. However, the tribunal concluded that the DCO told Mr Troicki that she could not advise him as to whether his reason for not providing a blood sample was valid, and that no such assurances were given by her.
"Accordingly, the tribunal determined that Mr Troicki's actions constituted a failure and a refusal to provide a blood sample, and that his explanation for not doing so did not constitute compelling justification under Article 2.3.
"However, the tribunal accepted that the stress that Mr Troicki was under at the time entitled him to mitigation under Article 10.5.2."