The New Zealand heavyweight tested positive in a drugs test administered the same day of his 11th-round defeat to UK boxer Fabio Wardley.
Fabio Wardley along with the New Zealander participated in a pulsating contest in London last October to determine the next mandatory WBO contender to undisputed world heavyweight champion Ukrainian champion Usyk.
Parker had been next in line to meet Oleksandr Usyk after stringing together a remarkable six-fight winning streak, however risked his contender position at stake during the bout and suffered a stoppage in round eleven.
An ordinary examination conducted on Joseph Parker through Vada the day he fought returned positive and leaves the veteran boxer in a difficult position to prove his innocence.
Parker's promotional company issued an announcement declaring: "Vada informed all relevant parties that Joseph Parker tested positive after a drug screening conducted on October 25th. As the investigation continues, no additional comment will be made for now."
Parker was crowned titleholder back in 2016 prior to he lost his championship belt via unanimous decision against Anthony Joshua in Wales two years later.
Parker remained a frequent visitor across the United Kingdom from that point, competing in eight bouts altogether in the UK and moving to Ireland for fight camps alongside highly regarded trainer Andy Lee over the past few years.
Under the tutelage of Lee, Parker bounced back from his 2022 loss against Joe Joyce to chalk up multiple wins positioning him front of the queue to challenge Usyk before he was defeated against Wardley.
After Parker returned an adverse finding when he fought Wardley, allegedly for cocaine, a probe about the test outcome is underway.
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