
Agnieszka Radwanska of Poland holds aloft the Billie Jean King Trophy after defeating Petra Kvitova of Czech Republic in the title match of the WTA Finals.

Kvitova of Czech Republic reacts to a point against Maria Sharapova in the way to a surprise victory over the Russian in the WTA Finals.

Sharapova of Russia looks dejected after slipping to a shock defeat to Kvitova in the semifinals.

Radwanska ended the hopes of Spain's Garbine Muguruza in the semifinals at the WTA Finals.

Day Six —
Muguruza beat Kvitova 6-4 4-6 7-5 at the WTA Finals in Singapore to win the White Group and progress to the semifinals.

Day Six —
But it wasn't all bad news for Kvitova, the two-time Wimbledon champion ...

Day Six —
She joined Muguruza in the last four when Lucie Safarova, pictured, topped Angelique Kerber in straight sets, 6-4 6-3.

Day Six —
Kerber's week began well when she downed Kvitova but then the German lost to Muguruza and Safarova.

Day Six —
In Saturday's semifinals, Sharapova, pictured, played Kvitova and Muguruza faces Radwanska.

Day Five —
That about sums it up for Simona Halep. She lost to Radwanska on Thursday and was eliminated at the WTA Finals.

Day Five —
A frustrated Halep, seen here with coach Darren Cahill, fell 7-6 (7-5) 6-1. The Romanian was the highest ranked player in the field at No. 2.

Day Five —
Sharapova knew she made the semifinals even before she played Flavia Pennetta but still beat the Italian 7-5 6-1, rallying from 4-2 down in the first.

Day Five —
Sharapova finished at 3-0 in the Red Group and progressed with Radwanska. Pennetta, meanwhile, played the final match of her career.

Day Four —
Kvitova bounced back from her opening defeat at the WTA Finals in Singapore by beating fellow Czech Lucie Safarova 7-5 7-5 on Wednesday.

Day Four —
Kvitova has now beaten her friend eight times in a row. Next month they will line up together against Russia in the Fed Cup final, seeking to give the Czech Republic a fourth title in five years.

Day Four —
Kvitova will play unbeaten Spanish second seed Muguruza in her final White Group match. The 22-year-old has two wins from two after beating Angelique Kerber 6-4 6-4 in Wednesday's second match.

Day Four —
Sixth seed Kerber, who would have reached the semis with victory over Muguruza, faces Safarova in her closing match.

Day Three —
Sharapova celebrates after beating top seed Halep 6-4 6-4 in their second Red Group round-robin match in Singapore.

Day Three —
Halep could have qualified for the semifinals with victory, but the Romanian lost seven out of eight games from 4-4 in the opening set and the Russian held off her late fightback.

Day Three —
Pennetta signs autographs for fans after defeating Radwanska 7-6 (7-5) 6-4 in Tuesday's earlier Red Group match. Italy's U.S. Open champion kept her semifinal hopes alive ahead of her closing match against Sharapova.

Day Three —
Radwanska led 5-3 in the opening set, and the Polish fifth seed saved three match points before her second defeat in three days.

Day Two —
Spain's rising star Muguruza opened her White Group campaign with a 6-3 7-6 (7-4) win against Safarova of the Czech Republic on Monday.

Safarova beat the 22-year-old in this year's French Open quarterfinals in their only other meeting, but the world No. 9 was sidelined by a debilitating bacterial infection after her first-round defeat at the U.S. Open.

Day Two —
Kvitova, who has also struggled with health issues this year, lost 6-2 7-6 (7-3) to Germany's Angelique Kerber in their opening White Group match.

Kerber had lost her previous four clashes with her fellow left-hander, who won the tournament in 2011 when it was held in Istanbul.

Day One —
Sharapova triumphed against Radwanska on Sunday in her first completed match since the Wimbledon semifinals. The world No. 4 pulled out with an arm injury during her return in Wuhan last month.

Day One —
Sharapova battled Radwanska for nearly three hours on Sunday before triumphing 4-6 6-3 6-4.

Day One —
World No. 2 Halep, meanwhile, needed just 70 minutes to thrash Pennetta 6-0 6-3.

Day One —
Pennetta, who will retire at the end of this season, was unable to regain the form that gave her a straight-sets victory over the 24-year-old in the U.S Open semis.