The New Zealand heavyweight returned an adverse finding during a drugs test carried out the very day he faced 11th-round stoppage versus UK boxer Fabio Wardley.
Wardley together with Parker participated in a pulsating encounter staged in the UK capital last October to determine the identity of the WBO mandatory challenger to unified heavyweight titleholder Ukrainian champion Usyk.
The fighter had been the primary candidate to meet the champion subsequent to putting together an impressive six-fight winning streak, but placed his mandatory challenger status on the line in London and suffered a stoppage in round eleven.
A standard screening conducted on the boxer via the Voluntary Anti-Doping Agency the day he fought returned positive which leaves Parker with a battle to demonstrate his cleanliness.
Parker's promotional company published a statement declaring: "The agency notified everyone involved regarding Joseph Parker returned an adverse finding after an anti-doping test administered on the 25th October. During the ongoing inquiry, no additional comment will be made at this time."
The New Zealand boxer was crowned titleholder back in 2016 before he was defeated for his championship belt via unanimous decision versus British star Joshua in Wales 24 months later.
Parker became a regular competitor across the United Kingdom since then, competing in eight bouts overall in Britain and moving to Ireland for preparation alongside highly regarded trainer former champion Lee during this period.
Under the tutelage of Lee, Parker recovered from the 2022 setback to Joe Joyce to achieve a string of victories positioning him as the top contender to meet Usyk prior to he lost to the British fighter.
Following Parker returned a positive test on the day of the Wardley fight, allegedly for cocaine, a probe into the findings is underway.
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