Singapore - Maria Sharapova reached the semi-finals of the WTA Finals and sent U.S. Open champion Flavia Pennetta into retirement by beating the Italian 7-5, 6-1 on Thursday.
The 33-year-old Pennetta was eliminated with the loss and was playing in her last career tournament, having announced at the U.S. Open she would retire at the end of the season.
Agnieszka Radwanska also reached the semi-finals by beating top-seeded Simona Halep 7-6 (5), 6-1 earlier.
Sharapova completed the round-robin stage 3-0, while Radwanska, Pennetta and Halep all finished at 1-2.
Radwanska advanced because of more sets won, as Pennetta had to win at least one set against Sharapova to reach the semi-finals.
Pennetta led 3-1 in the first set but Sharapova broke back in the eighth game and took control of the match.
Halep reached the final in her first WTA appearance last year but became the first player to be eliminated.
"I go home," Halep said. "I go to the holiday. It's OK. I think I had a good year this year."
Radwanska trailed 3-1 in the first set and then 5-1 in the tiebreaker before turning the match around. In the second set, Halep saved a break point to hold serve in the first game but won only one point in three more service games.
"I was done," Halep said of the first set. "No energy anymore. I was tired. I felt that I lost the chance to win the first set and probably I lost the chance to win the match in that moment."