Reigning world champion Lazaro Alvarez Estrada of Cuba was upset by Irish boxer John Joe Nevin in a semifinal bout Thursday at the London Games.
Alvarez Estrada, the top seed in the men's bantamweight draw, was dealt a 19-14 loss by Nevin, who will now face Great Britain's Luke Campbell in Saturday's gold medal match.
The Cuban favorite will have to settle for bronze along with Japan's Satoshi Shimizu, who dropped a 20-11 decision to Campbell. All boxers who lose in the semifinal round are awarded bronze medals.
No. 1 seeds also fell in the semifinals of three other weight divisions on Friday as flyweight Misha Aloian of Russia, welterweight Taras Shelestryuk of the Ukraine and Azerbaijani super heavyweight Magomedrasul Medzhidov all were upset.
Mongolia's Tugstsogt Nyambayar beat Aloian and will fight Cuba's Robeisy Ramirez Carrazana for gold, while Shelestryuk was defeated by Great Britain's Freddie Evans, who will face second-seeded Serik Sapiyev of Kazakhstan for the welterweight title. After beating Medzhidov, Italy's Roberto Cammarelle earned a place in the super heavy gold medal bout against British fighter Anthony Joshua.
In other action, the top seed remaining in the semifinals of the light flyweight, light welterweight, middleweight and heavyweight classes all moved onto their respective gold medal matches.
The Ukraine's Oleksandr Usyk, the No. 1 seed in the heavyweight draw, demolished Tervel Pulev of Bulgaria, 21-5, to earn a spot in the final round against Italy's Clemente Russo. The second-seed Italian posted a 15-13 win in his semifinal bout against Azerbaijan's Teymur Mammadov.
China's Zou Shiming also earned a right to fight for gold. The No. 1 seed in the flyweight class was tied with Paddy Barnes of Ireland at 15-15 after the third round, but Zou was awarded the decision on countback.
Zou, who also beat Barnes in the semifinals four years ago in Beijing, will face Thailand's Kaeo Pongprayoon for gold. Pongprayoon beat third-seeded David Ayrapetyan of Russia in the other semifinal bout.
The gold medalist in the light welterweight class will be determined in a match between second seed Denys Berinchyk of the Ukraine and Cuba's Roniel Iglesias Sotolongo, who earlier in the tournament knocked off top-seeded Everton dos Santos Lopes of Brazil.
Iglesias Sotolongo beat Vincenzo Mangiacapre of Italy by a 15-8 score and Berinchyk was 29-21 winner over Mongolia's Munk-Erdene Uranchimeg.
In the men's middleweight competition, Japan's Ryota Murata, the second seed, will square off against Esquiva Falcao Florentino of Brazil for gold. Murata beat Uzbekistan's Abbos Atoev and the fourth-seeded Falcao Florentino dispatched Great Britain's Anthony Ogogo.
The lightweight title match will pit Vasyl Lomachenko of the Ukraine against South Korea's Soonchul Han, while the light heavyweight gold will be determined by the winner of a bout between Egor Mekhontcev of Russia and Kazakhstan's Adilbek Niyazymbetov.