Alexander Povetkin knocks out stand-in opponent... hours after revelation Russian boxer failed drug test and loses title shot with Bermane Stiverne

Alexander Povetkin dominated and knocked out last-minute replacement opponent Johann Duhaupas — just hours after it emerged he had failed a drug test.

Povetkin had been due to fight Bermane Stiverne for the WBC interim world title on Saturday in Russia. 

But the Russian boxer tested positive for the banned muscle-building substance ostarine and his Haitian-Canadian opponent pulled out on the morning of the fight.

Alexander Povetkin dominated and knocked out replacement opponent Johann Duhaupas

Povetkin, who lost out on a world title shot, puts pressure on his 35-year-old French opponent 

World Boxing Council (WBC) president Mauricio Sulaiman had earlier said Povetkin failed a doping test and sanctioning for the heavyweight's title bout against Stiverne had been withdrawn. 

In a post on Twitter, Sulaiman says Povetkin tested positive for the banned muscle-building substance ostarine.

The Russian heavyweight lands a powerful left-handed punch on Duhaupas' chin 

Povetkin had been due to fight Bermane Stiverne for the WBC interim world title on Saturday

His stand-in opponent, Duhaupas, motionless on the canvas after being knocked out

It was Povetkin's second failed doping test this year.

He lost another title shot in May when he tested positive for meldonium shortly before a bout with Deontay Wilder.

On that occasion, the WBC accepted Povetkin's explanation that he had stopped taking the substance before it was banned for 2016.