Austria's Stefan Koubek has been banned for three months by the International Tennis Federation (ITF) after testing positive for a banned substance.
Koubek claims he did not knowingly take banned substances
The world number 60 failed a routine drugs test at the French Open in May but now plans to lodge an appeal.
Koubek, who blamed an injection given by an Austrian doctor to treat a wrist injury, said: "I have acted correctly."
The failed test will have no bearing on Austria's Davis Cup victory over Great Britain in September.
Koubek beat Greg Rusedski in the decisive rubber to relegate Britain from the Davis Cup World Group.
The Austrian tested positive for the banned substance triamcinolon acetonid at Roland Garros.
"The doctor assured me that no prohibited substances were in the medication," Koubek wrote in his diary on the www.tennisweb.at website.
"I sought treatment from a recognized sports physician who knows about the list of banned substances.
"And I even asked if the substance that he was giving me was 100% safe."
The ITF rejected Koubek's defence of no fault or negligence, but it accepted there had been no intent on his part to enhance performance.
The 27-year-old's results from the French Open, where he reached the third round, were declared invalid and his ranking points and prize money withdrawn.
Other results obtained since Roland Garros are unaffected.
Unless an appeal is successful, Koubek will be banned until 21 March.
"A three-month ban would mean that I not only will miss the Australian Open, but also the Davis Cup in Australia," said Koubek.