Lucie Safarova grabbed the last spot at the WTA finals on Thursday after her last rival Carla Suarez Navarro lost to a qualifier at the Kremlin Cup.
Suarez Navarro could have qualified for the season-ending tournament in Singapore by reaching the final in Moscow but was beaten 6-1 6-2 by Russia's Daria Kasatkina in the quarter-finals.
Suarez Navarro landed just 56 per cent of her first serves as she was dismissed in less than an hour by Kasatkina, who at 104th in the world is ranked 90 places below her Spanish opponent.
Suarez Navarro said she had "a really bad day" against Kasatkina but denied she was feeling the pressure of having to qualify for next week's finals.
"I don't think about Singapore at all this match," she said. "I just tried to play good, to be focused on my game, but she played good tactically and I couldn't be aggressive."
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Czech player Safarova had lost in the first round in Moscow to reigning champion Anastasia Pavlyuchenkova.
In Singapore, she joins Simona Halep, Garbine Muguruza, Maria Sharapova, Petra Kvitova, Agnieszka Radwanska, Angelique Kerber and Flavia Pennetta.
In the Moscow semi-finals, Kasatkina will face one of two fellow Russians, either reigning Kremlin Cup champion Anastasia Pavlyuchenkova or Margarita Gasparyan.
The other semi-final will pit Russia's Svetlana Kuznetsova against Ukraine's Lesia Tsurenko.
Two-time grand slam champion Kuznetsova had a tough start against Latvian qualifier Anastasija Sevastova 5-7 6-1 6-3. Tsurenko had a walkover when third-seeded Pennetta withdrew Wednesday citing a leg injury.
In the men's draw, France's Lucas Pouille won his second-round match against Spain's Daniel Gimeno-Traver 6-1 7-6 (7-5). He meets second-seeded Roberto Bautista Agut of Spain in the quarter-finals.
