Jelena Jankovic remained on course to win a third title in 2009 as she made light work of Russian Elena Vesnina in Tokyo.
Serbian Jankovic, 24, eased into the quarter-finals of the Toray Pan Pacific Open, at the expense of Vesnina who retired injured when trailing 6-1 3-0.
After wins in Marbella and Cincinnati earlier in the year, seventh seed Jankovic finds herself the firm favourite in the Japanese capital after early exits for the players ranked ahead of her.
The tournament has seen shock early defeats for defending champion Dinara Safina, Venus Williams, Elena Dementieva, Caroline Wozniacki, Svetlana Kuznetsova and Vera Zvonareva.
France's Marion Bartoli will take on Jankovic in the last eight after recovering from an unconvincing start to beat Russian Anastasia Pavlyuchenkova 4-6 6-2 7-5.
Former world number one Maria Sharapova later won an all-Russian clash with Alisa Kleybanova 2-6 6-2 6-2 to reach the last eight.