Jankovic is looking forward to performing in Doha
Jelena Jankovic has qualified for next week's season-ending WTA Championships after Vera Zvonareva lost to Tsvetana Pironkova 6-0 6-2 in the Kremlin Cup.
Jankovic is five points ahead of Zvonareva in the Doha race and will fill the final berth in the event.
Serena and Venus Williams, Dinara Safina, Svetlana Kuznetsova, Elena Dementieva, Caroline Wozniacki and Victoria Azarenka also qualified.
Zvonareva and Agnieszka Radwanska will go to Doha as reserves.
Serbia's Jankovic, the defending Kremlin Cup champion, followed up her guaranteed qualification by beating Lucie Safarova of the Czech Republic 7-6 (7-5) 6-3 in her second-round match in Moscow.
Jankovic, a former world number one, said: "I am really happy about making it to the WTA Championships for the third time in my career.
"It is always a nice feeling to end the season playing in the Championships as one of the best eight players in the world. I'm looking forward to returning to Doha and playing some great matches."
Bulgarian qualifier Pironkova, the world number 126, secured only her fourth win on tour this year and her first since April.
The 22-year-old will now contest her first quarter-final of the season, where she will meet Ukraine's Alona Bondarenko.
The defeated Zvonareva, who struggled for form in the opening set and when trailing 3-2 in the second was forced to call for a trainer to treat her knees, admitted she was not feeling 100%.
"I'm not in my best shape now and to beat (Pironkova) I should have played more attentively," the 25-year-old said.
"Maybe I'm even happy. Finally I will have time to restore my health and start the new season in full strength."
In other second-round action, eighth seed Francesca Schiavone of Italy beat Romania's Monica Niculescu 6-2 7-5 and Russian Maria Kirilenko overcame Canadian Aleksandra Wozniak 6-4 6-3.
The Sony Ericsson Championship features the top eight on the Race to Doha standings, playing in a round-robin format before the tournament enters a knockout phase.
In the men's event in Moscow, sixth seed Janko Tipsarevic of Serbia progressed after Belgium's Christophe Rochus lost the first set and was forced to retire when trailing 2-1 in the second.
In other matches, American Robby Ginepri beat Spaniard Marcel Granollers 7-6 (7-5) 6-0, Kazakhstan's Mikhail Kukushkin saw off American Wayne Odesnik 6-3 6-4 and Ukraine's Iliya Marchenko beat Kazakhstan's Andrey Golubev 6-1 1-6 6-4.