(Reuters) - 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 semi-finals of an ATP 250 event in Pune, India earlier this year, did not provide further details about the banned substance.