Defending champion Tamarine Tanasugarn won a straight sets Wednesday and advanced to the quarterfinals of the HP Japan Women\'s Open tennis tournament. Tanasugarn, who has played mostly on the ITF Tour since winning in Osaka last year, beat Mathilde Johansson 6-2, 6-4 in a second-round match. Tanasugarn had a solid service game, dropping serve once and winning 71 percent of the points on serve. She next goes against third-seeded Angelique Kerber, who was a 6-1, 6-3 winner over Olga Govortsova in her second-round match. Kerber had six service breaks in eight receiving games. Zheng Jie posted the upset of the day with a 7-5, 6-3 victory over fifth-seeded Jarmila Gajdosova. Zheng won as many points -- 31-31 -- as Gajdosova when Gajdosova served. That led to five service breaks for Zheng. No. 4-seeded Petra Cetkovska blew past Erika Sema 6-0, 6-3 in 60 minutes. Cetkovska won 70 percent of the points on serve. Cetkovska and Zheng will play in a quarterfinal Friday. Vania King defeated Jill Craybas 6-1, 3-6, 6-1 in the tournament\'s final first-round match. King draws second-seeded Marion Bartoli in the second round.