Ana Ivanovic's late-season slump continued today as she suffered a 6-1 1-6 6-2 defeat by Russian Nadia Petrova during their second-round match at the Pacific Open.
The world's third-ranked player, Ivanovic has been off-key since winning her first Grand Slam title at the French Open in June. The Serb was ousted in the third round at Wimbledon before suffering a similar fate in Montreal.
Ivanovic failed to bounce back at the US Open, losing to qualifier Julie Coin of France in the second round.
Her woes continued at this Japanese hardcourt event. Ivanovic had her serve broken three times in the first set by Petrova but rebounded in the second set by winning 75% of her service points.
But Petrova, the world number 20, dominated Ivanovic in the third set, firing a trio of aces while winning 84% of her service points.
Petrova advanced to face sixth seed Agnieszka Radwanska of Poland, who claimed a 6-2 6-3 victory over France's Marion Bartoli during their second-round match.
The top-seeded Jelena Jankovic took the first step toward forgetting her defeat at the US Open by posting a carefree 6-2 6-1 victory over Flavia Pennetta in her first match at the Tier I event.
Jankovic, the world number two, was one victory away from claiming her first career major title 11 days ago before losing to Serena Williams in the final at Flushing Meadows.
However, after receiving a first-round bye here, the Serb ousted Pennetta to claim a spot in the quarter-finals.
Jankovic fired five aces and capitalised on all four break points, needing just more than an hour to see off the Italian.
Despite winning one tournament this season - the clay court event in Rome in May - Jankovic, 23, improved to 51-15 with her victory. She next will face fifth-seeded Russian Svetlana Kuznetsova, who eased to a 6-1 6-1 triumph in 45 minutes against wild card Ayumi Morita of Japan during their second-round match.
Third-seeded Elena Dementieva also cruised to victory, claiming a 6-0 6-3 win over France's Alize Cornet.
Russia's Dementieva, the world number four, has been on fire of late, advancing to the semi-finals in six of her last eight tournaments. That run includes a gold medal at the Beijing Olympics and finals appearances at Istanbul and Berlin.
The 26-year-old took advantage of five double faults by Cornet, winning the first career meeting against the Frenchwoman in 69 minutes despite having play stopped for a short period due to rain.