PRAGUE, Czech Republic -- Czech tennis player Ivo Minar tested positive for a banned substance after a Davis Cup match.
Czech Tennis Association president Ivo Kaderka said on Monday that the sample was taken after a Davis Cup quarterfinal victory over Argentina on July 10-12.
Kaderka said Minar was taking an unspecified supplement that apparently contained a derivative of the banned stimulant pseudoephedrine.
The International Tennis Federation in London said it had no comment.
The 25-year-old Minar, who is ranked 66th, denied deliberate doping.
"I have never consciously taken a banned substance," he said in a statement sent to the CTK news agency. "This is why I rejected the accusation of doping in my reaction sent to the ITF."
Minar cited an injury when he pulled out on Friday from the upcoming U.S. Open.
Kaderka said he interpreted Minar's decision to withdraw as an "offer to deal with the matter in a professional way," not an admission of guilt.
It's unclear whether Minar will be able to play in the Davis Cup semifinal against Croatia on Sept. 18-20.
Minar, who turned pro in 2002 and has never won an ATP Tour singles title, won a doubles tournament in Munich this year with Tomas Berdych.