Poland's Kamil Majchrzak said he had failed a drug test, adding that he did not knowingly take a banned substance and that the news came as "the biggest shock."
The 77th-ranked Majchrzak, who won the Challenger Tour event in Busan, South Korea in October and reached the semifinals of an ATP 250 event in Pune, India earlier this year, did not provide further details about the banned substance.
"I have some incredibly sad and difficult news to share with everyone. I have tested positive in anti-doping controls during October and November 2022," Majchrzak wrote in a post on Instagram on Thursday.
"Firstly, I have never, ever, knowingly taken any banned substance. At this moment I have no idea what has happened and this is the biggest shock.
"I have started the most difficult fight of my life - the fight to prove my innocence and to return to the sport I love."
The International Tennis Integrity Agency (ITIA) did not immediately respond to an emailed request for comment.
diately respond to an emailed request for comment.