NEW YORK, NY, USA - After two tight matches Wednesday, including one between the duos with the first and second most titles on the Sony Ericsson WTA Tour in 2009, the semifinals are now set in the doubles draw at the US Open.

In a battle that lived up to the hype, No.1 seeds Cara Black and Liezel Huber, who have five Tour titles this year, outlasted No.6 seeds Nuria Llagostera Vives and María José Martínez Sánchez, who have six. The third set was on serve all the way through until Black and Huber broke Martínez Sánchez's serve at 5-5, and then Black served it out for the 63 26 75 victory. Black and Huber are now 6-0 in the career series between the two teams, but they split sets in the last three matches, including in the quarters of Wimbledon earlier this summer. Black and Huber's semifinal foes will be No.3 seeds Samantha Stosur and Rennae Stubbs.

In Wednesday's other quarterfinal, fourth-seeded Serena and Venus Williams were tested, but got past 11th-seeded Yan Zi and Zheng Jie, 75 64. The sisters, who are now 2-1 against the Chinese duo, actually lost their first encounter with them, in the quarterfinals of the 2008 Australian Open, before getting revenge with a double bagel in the round of 16 at Wimbledon this year en route to the title. The Williamses, who have yet to drop a set in this tournament, next play 13th-seeded Alisa Kleybanova and Ekaterina Makarova.