Injured French star Marion Bartoli will need to recover quickly before she faces Christina McHale, who punched her ticket to the quarter-finals with a 4-6, 6-4, 6-4 win over Misaki Doi.
The top-seeded Bartoli struggled in a second round win Wednesday over American Vania King as she needed treatment on her left hip during the match.
The world number 10 is counting on solid hardcourt performances this summer in North American as she misses the London Olympics due to a longstanding feud with the national federation over her insistence that her father should be her only coach.
Bartoli spent Thursday in rehab with the hopes of being ready for Friday's quarter-final against McHale, one of two American Olympians in the quarters.
"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 Wednesday 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."
McHale showed her fighting qualities as she recovered to beat Doi on Thursday 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.
"I have to give credit to Misaki because she played really, really well." said McHale. "She made it hard for me. In the third set I started finding my rhythm more on my serve, which made it easier then for me to hold."
Serbia's former number one 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 number two Agnieszka, posted a 6-2, 6-1 win over American Melanie Oudin, who came into 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 Games. "To be honest, I didn't have any strategy because I never played her, so I didn't know what to expect.
"I was just focusing on myself and trying to do my best and go for my shots and keep the serve. I'm happy I did well."
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 winner.