TOKYO — Jelena Jankovic of Serbia advanced to the quarterfinals of the Toray Pan Pacific Open on Wednesday when Russia’s Elena Vesnina was forced to retire with a left thigh injury.

Jankovic was leading 6-1, 3-0 when the match was stopped.
The former world No. 1 is the highest seeded player remaining in the $2 million tournament.
“I don’t really think about that,” said Jankovic, seeded seventh. “I just think about my game and what I have to do on the court. I don’t want to put too much pressure on myself.”
Jankovic will meet France’s Marion Bartoli in the quarterfinals on Thursday.
Bartoli, seeded 14th, recovered from a set down to defeat Anastasia Pavlyuchenkova of Russia, 4-6, 6-2, 7-5.
Jankovic has lost to Bartoli twice this year, at the Australian Open and at Stanford.
Top-ranked Dinara Safina of Russia, Venus Williams and French Open champion Svetlana Kuznetsova all lost their opening matches Monday after first-round byes.
Former No. 1 Maria Sharapova, 25th in the world following shoulder surgery last October, was to play compatriot Alisa Kleybanova later Wednesday.