British boxer Amir Khan pulled off an emphatic 37-21 win over European champion Dimitar Stilianov to boost his chances of winning a medal in Athens.
The 17-year-old struggled at first against his southpaw foe from Bulgaria and was a point ahead after round one.
But Khan improved, shaking Stilianov with a combination and showing dazzling footwork and accuracy to pull clear.
Britain's lone boxer will now take on South Korean Baik Jong-Sub for a place in the Olympic semi-finals.
"My nerves have calmed and I'm more relaxed. By the last round, it was comfortable," said Khan.
"To beat the European champion is a great achievement. I knew I could beat him, but we had tactics and they worked.
"This gives me a lot of confidence, although I don't want to be too confident because my next fight will be hard."
Khan is bidding to become the youngest Olympic boxing champion since Floyd Patterson in 1952, but Cuban favourite Mario Kindelan is still lurking in the opposite half of the draw.
BBC Sport boxing commentator Richie Woodhall - a former bronze medallist - called Khan's display the best of the tournament so far and tipped him to reach the 60kg final.
"Stilianov is an excellent fighter and no-one pushes him around like that," he said.
"Khan will have too much for his next opponent and will go all the way to the gold-medal bout, where he will face Kindelan.
"That will be a 50-50 fight."