Serbia's Viktor Troicki, a former world number 12 and a Davis Cup winner in 2010, was banned for 18 months on Thursday for flouting doping rules, the International Tennis Federation (ITF) said.
The 27-year-old Troicki was found guilty of failing to provide a blood sample during a drugs test at the Monte Carlo Masters in April.
"Mr Troicki provided a urine sample, but did not provide a blood sample," said an ITF statement.
"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.
"The tribunal determined that he is suspended from participation for a period of 18 months, and so ending at midnight on 24 January 2015."