Top seed and former title holder John Isner downed Chung Hyeon 7-6 (7-5), 6-4 Friday to book a semifinal clash with defending champion Jack Sock at the ATP claycourt tournament in Houston Friday. Isner, who lifted the trophy in 2013, saved all seven break points he against the rising South Korean star, firing 14 aces and winning 58 percent of his second serve points. The US veteran was solid when it mattered most against the 19-year-old Chung, voted last year's Most Improved Player by his peers. "That one game in the first set, I was down four break points," Isner said. "Serving at 4-3 (in the second), I was down three break points and I had to hit a stab volley on one of them. That was huge. He played a good return game." Although he pulled off the win, Isner said he expected to see Chung continue to rise. Isner set up a clash with another young standout in Sock, who defeated seventh-seeded Cypriot Marcos Baghdatis 6-4, 6-4. Sock, seeded fourth, converted two of his eight break point opportunities and that was enough to extend his Houston winning streak to seven matches. Former champion Juan Monaco of Argentina ousted fifth-seeded American Sam Querrey 6-4, 6-4 to book a semifinal against third-seeded Spaniard Feliciano Lopez, a 6-2, 6-3 winner over American Tim Smyczek. Monaco will face a tough task against Lopez, who leads their career head-to-head 4-2 and said after downing Smyczek that he was gaining confidence with every match. Kerber moves into last 4 In Los Angeles, Australian Open champion Angelique Kerber moved a step closer to her second straight Volvo Car Open title, reaching the semifinals with a 6-2, 6-3 victory over Irina Camelia Begu Friday. Kerber will face No. 7 seed Sloane Stephens Saturday for a spot in the championship match. The 23-year-old American beat 14th-seeded Daria Kasatkina of Russia 6-1, 5-7, 7-5 and continue her best tournament run in six appearances. Russian qualifier Elena Vesnina, who toppled second-seeded Belinda Bencic in the second round, reached the semifinals with a 7-5, 6-4 victory over Germany's Laura Siegemund. Vesnina set up a meeting with fifth-seeded Italian Sara Errani — a 7-6 (7-2), 6-1 winner over Kazakhstan's Yulia Putintseva.
