Australia's Samantha Stosur has been dumped out of the East West Bank Classic after losing to Victoria Azarenka in the third round.
In a tight match, the eighth-seeded Belarussian prevailed in straight sets 6-4 7-6 (7-4).
Jelena Jankovic moved a step closer to becoming the new world number one on Thursday with a 6-3 6-2 victory over Hungary's Melinda Czink.
Currently the world number two, Jankovic had opportunities to become the top-ranked player at both the French Open and Wimbledon. She failed to seize those chances, however, unable to reach the championship match at either major.
While the stage here is a bit smaller, the opportunity to move atop the rankings once again has presented itself to the 23-year-old, who never has played in a Grand Slam final.
If Jankovic can win this Tier II event, she will overtake Ana Ivanovic as the new number one and become the 18th player in WTA history to rise to the top spot. Ivanovic, who became the world number one following her win at the French Open, is the defending champion of this event but opted not to participate this time around, leaving the door open for Jankovic, a semi-finalist here a year ago.
Jankovic, however, is not playing at 100 percent after suffering a left knee injury at Wimbledon. But she still advanced to meet last year's runner-up, number nine Nadia Petrova, who beat fifth-seeded Vera Zvonareva 6-4 7-5 on Thursday.
Appearing to be in good position to move into the quarter-finals, Anna Chakvetadze was upset by 14th-seeded Austrian Sybille Bammer 6-4 5-7 6-2, earlier in the day.
The third-seeded Russian has lacked consistency this season, but her performance during last year's summer hardcourt swing made her a legitimate candidate to win here. The 21-year-old captured 12 straight hardcourt matches following Wimbledon last year, claiming titles in Cincinnati and Stanford.
She was the highest remaining seed in her half of the draw following the late withdrawal of second-seeded American Serena Williams, who bowed out with a knee injury. Chakvetadze could not get past Bammer, who next will face 10th-seeded Flavia Pennetta of Italy, a 7-6 (7-5) 6-3 winner over Japan's Ai Sugiyama, in the round of eight.
A potentially formidable semi-final opponent for Jankovic, fourth-seeded Dinara Safina also booked her place in the round of eight Thursday, when she topped fellow Russian Alla Kudryavtseva 7-6 0-6 7-6 (7-3).
Safina has risen to ninth in the rankings following a run this spring that saw her win in Berlin and reach the French Open final. The 22-year-old had reached the championship in three consecutive events played prior to her third-round loss at Wimbledon.
Safina advanced to play eighth-seeded Azarenka of Belarus.
The only American remaining in the field is unseeded Bethanie Mattek, who ousted Olga Govortsova of Belarus. Mattek will take on China's Meng Yuan, who eliminated lucky loser Melanie South of England 6-2 6-3.
WTA East West Bank Classic, Los Angeles Results Day 4
Women’s Singles – Third Round
1-Jelena Jankovic (Serbia) def. Melinda Czink (Hungary) 6-3 6-2
8-Victoria Azarenka (Belarus) def. Samantha Stosur (Australia) 6-4 7-6 (7-4)
14-Sybille Bammer (Austria) def. 3-Anna Chakvetadze (Russia) 6-4 5-7 6-2
Yuan (China) def. Melanie South (Great Britain) 6-2 6-3
4-Dinara Safina (Russia) def. Alla Kudryavtseva (Russia) 7-6 (7-1) 0-6 7-6 (7-3)
10-Flavia Pennetta (Italy) def. Ai Sugiyama (Japan) 7-6 (7-5) 6-3
Bethanie Mattek (USA) def. Olga Govortsova (Belarus) 7-5 6-2