SINGAPORE - Agnieszka Radwanska remains on course to defend her title at the WTA Finals after she beat Karolina Pliskova 7-5, 6-3 on Friday (Oct 28) to secure the last semi-final slot.
Radwanska is the only one out of the four semi-finalists who has won the season-ending crown.
The 27-year-old Pole joins world No. 1 Angelique Kerber of Germany, Dominika Cibulkova of Slovakia and Svetlana Kuznetsova of Russia in the last four of the elite tournament, which features the eight best-performing singles players and doubles pairs of this year.
Kuznetsova will face Cibulkova in the first semi-final on Saturday (Oct 29), followed by Kerber versus Radwanska.
In a match which will see the winner progress to the semi-finals, it was Radwanska's game that was tidier. She made just eight unforced errors and 15 winners, while her Czech opponent finished with 27 winners but 29 unforced errors.
Despite playing with a tape strapped over her right shoulder and forearm, Pliskova, 24, dictated play with her powerful strokes and dominated the early rallies to earn an early break in the first set.
But it did not take long for Radwanska to read Pliskova's serve, which is her strongest weapon. Pliskova, the US Open finalist and world No. 5, struck six aces in the match for a total of 530 aces this year, or 206 more than second-placed Serena Williams.
Radwanska hit back with her strong returning game and superior retrieving ability. The world No. 3 entered the tournament with the third-highest percentage of return games won (49.3 per cent) among the players this year.
With the win, Radwanska also extended her mastery over Pliskova to seven matches. Pliskova has yet to win a set against Radwanska.
In the earlier round-robin match, Garbine Muguruza bowed out of the tournament with a win.
The 23-year-old world No. 6 dealt Kuznetsova her first loss of the tournament, beating the Russian 3-6, 6-0, 6-1. Muguruza also denied her opponent of reaching a milestone of 600 career victories.
But the loss did not dent Kuznetsova's semi-finals hopes at all, as she had already been assured of finishing top of the White Group.
Muguruza, last year's semi-finalist, recorded just her seventh win in her past 14 matches.
The powerful baseliner has struggled with her form after winning her first Grand Slam at the French Open in June.
Muguruza explained why she looked emotional after the match. She said: "It was very emotional for me to be here, and then the way the matches went, and I couldn't make it (to the semi-finals). It's been a hard year for me, for sure.
"I was not winning matches, so it created a lot of frustration. All these responsibilities, all these emotions were hard for me to deal with."
After dropping the first set, Muguruza stormed back to reel off 10 consecutive games to take a 4-0 lead in the third set.
Unlike Kuznetsova's previous two matches which stretched over two hours each, this encounter did not go the distance. Kuznetsova has the WTA Tour leading 22 three-set wins this year.