Victoria Azarenka has defeated China’s Li Na at the $4.9 million WTA Championships in Istanbul, a result that ensures the Belarusian holds the world No. 1 spot at the end of the season.
Azarenka completed a 7-6(4), 6-3 win over Li Na in her final group stage match to book a semifinal encounter with world No. 2 Sharapova, who remains undefeated at the tournament but has lost four of five matches against Azarenka this year.
Azarenka first reached top of the rankings since winning the Australian Open, her first Grand Slam singles title.
The Belarusian lost her first place to Maria Sharapova in June, when the Russian won the French Open, but regained it after Wimbledon.
"It's a dream come true and I feel great," Azarenka said after the match. "Now I just want to play my last matches of the year and then after that I can relax and enjoy this moment more."
Li started the match aggressively breaking the first serve of her opponent but then slowed down and lost the first set on a tie break.
Unforced errors in the second set wrote off Li’s hopes on getting through the round robin stage after failure on her debut last year.
Elsewhere, Agnieszka Radwanska battled past Italy’s Sara Errani to reach the semifinal after the longest match in the WTA Championships history.
Radwanska grabbed a (6)6-8, 7-5, 6-4 comeback win in three hours and 29 minutes, five minutes longer the previous record set by Belgium’s Justine Henin and Sharapova in the 2007 final.
The match saw 18 breaks of serve and 90 unforced errors.
The Polish player will now meet Serena Williams of the U.S., who has won all three group matches without dropping a set.
"I will do everything in my power to get as much treatment as possible and to go on court tomorrow in one piece," said Radwanska, who lost to Williams in their three previous clashes.
"Pretty much, I have nothing to lose playing Serena. She's a great champion and playing great tennis the last couple of weeks and months. So I'm just going to go on court and enjoy."
Both semifinals take place Saturday.