Andre Ward from the USA scored a huge upset in the light-heavyweight quarterfinals by out-pointing double world and European champion Eygeny Makarenko.
The Russian just could not make good use of his longer jab against the smaller American, who worked hard to get inside and build up an early lead and eventually run out the winner by 23-16.
Ward will now meet Uzbekistan southpaw Utkirbek Haydarov, who squeezed home in a battle of the punchers against Turk Ihsan Yildirim by 16-11.
The other half of the draw saw local boxer Elias Pavlidis fail to be the first Greek boxer to win a medal in the boxing tournament when he was prevented from continuing against Ahmed Ismail due to a cut over his left eye. Pavlidis was ahead on points when the referee stopped the bout. Pavlidis' loss was Ismail's gain as he became the first Egyptian boxer to win an Olympic boxing medal.
The last Quarterfinal of the night saw Magomed Aripgadjiev from Belarus out-point Chinese boxer Lei Yuping by 27-18 to set up a clash with Ismail.