The preliminary rounds of Olympic boxing have come to an end in Athens. Beginning on Sunday, boxers who win their bouts will advance to the semi-finals and are guaranteed a medal (two bronze medals are awarded, one to each semi-final loser). Four Americans are still in the hunt for medals: the two Andres, Dirrell and Ward and big men Devin Vargas and Jason Estrada. On Saturday, American boxers had mixed results. middleweight Andre Dirrell TKO’d Nabil Kassel of Algeria in the second round. To earn an Olympic medal, however, Dirrell will have to defeat the Cuban middleweight, Yordani Despaigne Herrera, who advanced over a Hungarian foe. Not faring as well as Dirrell was flyweight Ron Siler who ignored his jab and lost to Tulashboy Doniyorov of Uzbekistan, 45-22. In flyweight bouts, France’s Jerome Thomas (a bronze medalist in the 2000 Olympics) decisioned Dominican, Juan C. Payano, 36-17 and Cuban Yuriorkis Gamboa Toledano barely beat a very tough Thai opponent, Somjit Jongjohor, 26-21. In the light flyweight class, Najah Ali of Iraq could not produce a second upset win, and was eliminated by Aleksan Nalbandyan of Armenia, 24-11. After falling behind early, Ali gamely tried to knock out Nalbandyan, and was able to bloody his lip. Cuba made it two wins over two Thais on Friday when light fly Yan Bhartelemy Varela outpointed Suban Pannon, 23-14.