Joseph Parker returned an adverse finding as part of a anti-doping examination administered on the day he faced 11th-round loss against English fighter Fabio Wardley.
Wardley and Parker were part of a thrilling bout staged in the UK capital last October to establish the next mandatory WBO contender to undisputed world heavyweight champion Oleksandr Usyk.
Parker had been the primary candidate to meet Usyk following stringing together a notable six wins in a row, but put his shot at the title on the line in London and experienced an 11th-round stoppage.
A routine test given to Parker through Vada the day he fought returned positive and now leaves the veteran boxer in a difficult position to clear his name.
The boxer's representatives published a communique stating: "Vada alerted all relevant parties about Parker had a positive result after a doping test carried out on October 25th. As the investigation continues, no further statements are planned currently."
Joseph Parker earned the title of world champion six years ago before he lost his WBO belt through a points decision against Anthony Joshua in Wales two years later.
Parker has been an active participant on British soil after that, fighting eight times overall in the UK and moving to the Irish capital for training camps alongside respected coach Andy Lee in recent years.
Coached by Andy Lee, Joseph Parker recovered from his 2022 loss versus Joe Joyce to chalk up a string of victories that placed him as the top contender to face Oleksandr Usyk prior to he lost to the British fighter.
Following the boxer produced an adverse finding on the day of the Wardley fight, reportedly involving cocaine, an inquiry into the findings has been started.
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