Defending U.S. Open champion Novak Djokovic and David Ferrer have advanced to the semifinals after winning their quarterfinal matches on Thursday. Second-seeded Djokovic of Serbia beat Argentina’s seventh-ranked Juan Martin del Potro 6-2, 7-6 (3), 6-4, and fourth-seeded Ferrer of Spain downed eighth-ranked Serb Janko Tipsarevic 6-3, 6-7 (5), 2-6, 6-3, 7-6 (4).
