Second seed Maria Sharapova lost out of the WTA Finals despite a win over Poland’s Agnieszka Radwanska on Friday.
The Russian missed three match points as he conceded a second set tie-breaker to Radwanska but closed out the contest 7-5 6-7 (4-7) 6-2 after three hours and nine minutes.
The result also meant Sharapova, who would have advanced in Singapore had she not dropped a set in the last of her round robin match, had missed her slim chance for a maiden year-end No. 1 ranking.
“I got the job done,” Sharapova said. “I know I’m not moving forward, but I’m proud of that effort and to finish the year off on this way.
“I will not be chasing the number one ranking next season. I think adding more Grand Slam is the top priority.”
Caroline Wozniacki continued her impressive form with a 6-2 6-3 win over Petra Kvitova.
Wozniacki, who was already sure of a place in the WTA Finals semi-finals prior to Friday, and Radwanska are the two qualifiers from the White Group, while Wimbledon champion Kvitova and French Open champion Sharapova are out.
In the last singles match on Friday, Ana Ivanovic beat Simona Halep 7-6(9-7) 3-6 6-3, but failed to progress into the semis having dropped a set against the Romanian.
The Serb, whose other win in Singapore came against No.5-ranked Eugenie Bouchard earlier in the week, rallied from 2-5 down to win the opening set en route to just her 3rd victory over a multiple Top 5 player at the same tournament.
Halep, who has already qualified for the semi-finals by virtue of Thursday’s result, is joined in the Red Group by Williams in the semi-finals, while Ivanovic and Bouchard are out of the WTA Finals.
The line-up for the semi-finals in Singapore is thus complete with Williams setting up a rematch of the US Open final against her bestie Wozniacki and Simona Halep up against Agnieszka Radwanska.