Cuba suffered their worst night of the Games in the Olympic boxing ring yesterday as four medal hopes, including Juan Hernandez Sierra, the man who was denied a gold medal by Michael Carruth in 1992, were beaten in the quarter-finals.

Hernandez Sierra, who was out-pointed by Carruth in Barcelona in 1992, and again had to settle for silver in Atlanta, moved up a division from welterweight to light-middleweight for Sydney, but was taken out by the unfancied Yermakhan Ibraimov of Kazakhstan, who beat him 16-9.

Cuba's awesome super-heavyweight Alexis Rubalcaba, at six foot eight inches the biggest fighter at the Games, forced another Kazakh, Mukhtarkhan Dildabekov, to take three standing counts in their bout, but was outsmarted and lost 25-12.

Rubalcaba, the lumbering man-mountain who can be either lethal or lethargic depending on his mood, was also upset on points in the 1996 quarter-finals by Tongan Paea Wolfgramm. He had knocked out his first opponent but was out-thought, out-boxed and fortunate not to be outclassed, despite a seven-inch height advantage. Flyweight Manuel Mantilla, who had looked impressive in his opening bouts, lost 19-8 to Wijan Ponlid of Thailand in a bad tempered match, while featherweight Yosvany Aguilera also failed to make the medals, losing 17-12 to Kamil Dzamalutdinov of Russia. That left Cuba with a final tally of six semi-finalists, one fewer than Russia. Ukraine have five boxers remaining, while Kazakhstan and the United States have four each.

The United States's most impressive victory came from featherweight Ricardo "Rocky" Juarez, who out-classed the Atlanta gold medallist, Somluck Kamsing of Thailand, forcing the referee to stop the fight in the fourth round.