Serbia took a major step towards reaching the semi-finals by outlasting the host USA in a marathon five-set victory in Saturday's doubles competition of their Davis Cup tie. Ilija Bozoljac and Nenad Zimonjic shocked the top-ranked doubles team of Bob and Mike Bryan 7-6 (7/5), 7-6 (7/1), 5-7, 4-6, 15-13 to give Serbia a 2-1 lead in their best-of-five tie heading into a pair of Sunday's reverse singles matches. World No. 1 and reigning Aussie Open champ Novak Djokovic can send Serbia into the semis with a win Sunday over American Sam Querrey, who is ranked 20th in the world.

Novak Djokovic got Serbia off to a hot start, but American Sam Querrey's gritty victory over Viktor Troicki saw the United States pull level on the opening day of their Davis Cup World Group quarter-final tie. World No. 1 Djokovic beat big-serving John Isner in straight sets in the first singles match, recovering from an early break in the first set en route to a 7-6 (7/5), 6-2, 7-5 triumph. The Serbian player saved the only break point he faced in the third set -- in the second game -- and broke Isner at love for a 6-5 advantage.

Lukas Rosol gave defending champions the Czech Republic a commanding 2-0 lead in their Davis Cup quarter-final clash with hosts Kazakhstan on Friday, battling back from a set down to beat Andrey Golubev. World No. 63 Rosol won 4-6, 6-4, 6-2, 7-6 (8/6) in two hours 41 minutes in his first ever head-to-head clash with Golubev, who is ranked 205th in the ATP world rankings. Jan Hajek had gained the first point of the best-of-five match tie for the Czechs when he beat Mikhail Kukushkin 6-3, 6-2, 6-4.

World No. 1 Novak Djokovic beat big-serving John Isner in straight sets to give Serbia a 1-0 lead over the United States in their Davis Cup World Group quarter-final on Friday. Djokovic defeated Isner 7-6 (7/5), 6-2, 7-5, recovering from an early break in the opening set and taking control from there. The Serbian player saved the only break point he faced in the third set -- in the second game -- and broke Isner at love for a 6-5 advantage.