Jelena Jankovic remained on course to take over the No.1 ranking from compatriot Ana Ivanovic with a 6-3 6-2 victory over Melinda Czink of Hungary at the East West Bank Classic.
In the match against lucky loser Czink, Jankovic's serve was much better than usual.
"If I could hit this serve every day like that, my life would be so much easier," said J.J., laughing.
Jankovic is playing her first tournament since injuring her knee at Wimbledon last month.
"There's no pain and I'm really happy about that. My legs are a little bit hurting. I'm not used to playing matches every day and playing after not doing anything for two weeks. Now it's time to get in shape."
Still, Jankovic is wearing a tape on her knee.
"Without the tape, it would be a risk because the knee is still fragile," she said.
There were two upsets in Los Angeles on Thursday. Third-seeded Anna Chakvetadze was defeated by 14th-seeded Sybille Bammer 6-4 5-7 6-2, while fifth seed Vera Zvonareva lost 6-4 7-5 to last year's runner-up Nadia Petrova.