Top seed Marion Bartoli is attempting to overcome a hip problem in time for her California WTA quarter-final against Christina McHale, who had a 4-6 6-4 6-4 win over Misaki Doi on Thursday.

Bartoli struggled in a second-round win Wednesday over American Vania King as she needed treatment on her left hip during the match.

“I will be able to rest and have good work on it from the physio and get my whole body loose and relaxed,” Bartoli said after her late-night win which included a staggering 18 double-faults.

“It is great to have a day off, that’s for sure. But I will have to figure out why my serve is not on right now.”

American Olympian McHale showed her fighting qualities as she recovered to beat Doi after nearly three hours.

Japan’s Doi put McHale under pressure on serve, but the American saved 16 of a massive 19 break chances to reach her second quarter-final of the season after Doha.

Serbia’s former No.1 Jelena Jankovic rescued her opening match to get past Hungary’s Melina Czink 2-6 6-4 6-4 with six aces and four breaks of serve in the two-and-a-quarter-hour battle.

Jankovic, who owns a house in the area, reversed a disheartening trend of opening losses which stretched back to June.

Unseeded Ursula Radwanska, younger sister of Wimbledon finalist and world No.2 Agnieszka, posted a 6-2 6-1 win over American Melanie Oudin, who entered the draw as a lucky loser from qualifying.

Radwanska needed just 65 minutes to advance, going through with four aces and five breaks of her opponent.

“I was playing very good today, and serving especially well,” said Radwanska, who will play singles plus doubles with her sister for Poland at the London Games.

Second seed Dominika Cibulkova of Slovakia defeated New Zealand’s Marina Erakovic 6-2 6-4.

“In the first set, I was playing well and relaxed. In the second, I started to make it a little bit tougher than it should be. I was really happy to close it in the second. It was pretty good today,” said the Slovak.