BEIJING — Demetrius Andrade started out in an indecisive panic, as if he was certain the judges would refuse to score his punches even if he threw them. The American welterweight then stormed from the Olympic ring after the bell, even before his South Korean opponent's arm was raised.

Kazakhstan's Serik Sapiyev handled his own narrow loss to Thailand's Manus Boonjumnong with a bit more serenity, yet both world champions got the same sad result: They're going home from the Olympics without a medal.

South Korean Kim Jung-joo and Boonjumnong joined three Cuban boxers and Chinese welterweight Hanati Silamu with quarterfinal victories Sunday night. The wins set the Olympic tournament's first three semifinal fields, guaranteeing medals to every winner.

They won't be joined by Andrade or Sapiyev, the seventh and eighth world champions to lose before medal competition, or Gennady Kovalev, the eighth Russian to fall. Clemente Russo, the Italian heavyweight who won the night's final bout, is the only world champion so far guaranteed to add Olympic hardware to his title from last November in Chicago.

Andrade was one of just two Americans left in the Olympic field. Thanks to heavyweight Deontay Wilder's victory on punch statistics in a bout that finished in a 10-all tie with Morocco's Mohamed Arjaoui, the U.S. won't leave an Olympics empty-handed for the first time — but Wilder's single medal is the lowest total in team history.

"I don't want the world to remember Team USA as being failures," Wilder said.

With a week still left in the Beijing Games, it's already too late to stop that. But with so many surprising results in these Olympics, Andrade's loss to Kim, a bronze medalist in Athens, hardly seemed unlikely, despite Andrade's lofty international ranking and strong first two bouts.

Andrade controlled the action for much of his 11-9 defeat, but repeatedly failed to land scoring punches against his defensive, counterpunching foe. After the bell, he rested his head on the rope in frustrated exhaustion before looking up to the stands at his father.

Paul Andrade yelled, "That's all right, Boo Boo," as he pounded his chest and held his arms open wide.

"You know what was going through my mind?" Andrade asked. "I said, 'Damn, they might pull a Jones on me.'"

Roy Jones Jr.'s championship-bout loss to South Korea's Park Si-hun at the 1988 Seoul Games was so egregiously incorrect that it led to the introduction of computer scoring in amateur boxing. Most observers — particularly Kim's joyous camp — thought Andrade's loss was not in that category.

Andrade then temporarily lost his class, leaving the ring before the formal verdict.

"It was no disrespect to the fighter, but there was no point for me to be in there," Andrade said.

The class of Workers' Gymnasium still belongs to Cuba, which sent three fighters through to medal competition. Heavyweight Osmai Acosta, welterweight Carlos Banteaux and light welterweight Roniel Iglesias finished their opponents without putting anything in the hands of judges.

Iglesias beat Kovalev, who became the eighth Russian boxer to lose before the medal round, joining three world champions in the most improbable team-wide collapse in recent Olympic boxing history.

At least heavyweight Rakhim Chakhkiev guaranteed one medal to the Russians with a win over France's John Mbumba.

Iglesias, a 20-year-old dynamo, handled Kovalev with an ease that would have been surprising before Russia's profound flop in Beijing.

"I had some pressure because it was going to be the first medal for Cuba here, but the team prepares me very well," Iglesias said. "I'm prepared to beat the Olympic champion or the world champion."

Iglesias' next fight is against Boonjumnong, the defending Olympic champion light welterweight who began the session with a 7-5 win over Sapiyev. Boonjumnong said he spent two years partying after winning an unlikely gold in Athens, and the Thai fighter collapsed face-first with relief at the buzzer.

Light flyweight Zou Shiming's bronze medal in Athens was China's first Olympic boxing medal, but Hanati doubled his nation's total with his 14-4 win over the Bahamas' Toureano Johnson. What's more, five of Hanati's teammates — including Zou, the two-time world champion — could join him over the next three days.

And after several days of whining from Americans about the Olympic judging, Wilder received two good breaks from those same judges.

Arjaoui received a two-point penalty with 55 seconds left for head-butting, and the points moved Wilder from one point behind to one point ahead. Arjaoui then fought back to tie it in the closing moments, but Wilder finished with a higher average score from three of the five ringside judges.

Wilder was as surprised as Arjaoui, who collapsed in tears, when the referee raised his hand.

"I thought they were going to give it to him," Wilder said. "These judges have not been fair, particularly when it comes to the Americans."