Azarenka locks up year-end No. 1 spot

Victoria Azarenka needed to win two matches this week to clinch the year-end No. 1 ranking, and that's exactly what she did at the season-ending WTA Championships.

Azarenka (2-1) secured a berth in the semifinals in Istanbul by getting past eighth-seeded Chinese star Li Na, who went 1-2 this week, 7-6 (7-4), 6-3 in 1 hour, 39 minutes on Day 4 of this prestigious event.

The 23-year-old Belarusian becomes the 11th woman to finish the year at No. 1 since the rankings began in 1975.

A relieved Azarenka said, "I feel great. I mean, honestly, it's a dream coming true."

This week's top-four seeds all managed to land in the semis.

Azarenka's semifinal opponent on Saturday will be Russian star Maria Sharapova, who also posted a round-robin win on Friday. Azarenka beat Sharapova in this year's Australian Open final and is a dominant 4-1 versus the Russian in 2012, including a 3-1 record in four finals. Azarenka leads their all-time series, 7-4.

The Australian Open champion Azarenka was last year's WTA Championships runner-up to Czech left-hander Petra Kvitova.

Meanwhile, the French Open champion Sharapova went 3-0 in her round-robin matches this week.

The second-seeded former world No. 1 star breezed past ninth-seeded replacement Samantha Stosur 6-0, 6-3 indoors at Sinan Erdem Dome on Friday. The sturdy Aussie Stosur went 0-2 in her round-robin affairs after replacing the ill 2011 WTA Championships titlist Kvitova in the elite eight-player field on Wednesday.

The 2004 champion and 2007 WTA Championships runner-up Sharapova captured this week's four-player White Group, which also featured Wimbledon runner-up Agnieszka Radwanska (2-1) and French Open runner-up Sara Errani (1-2). The fourth-seeded Radwanska joined Azarenka, Sharapova and Serena Williams in the semis by outlasting the seventh-seeded Italian Errani 6-7 (6-8), 7-5, 6-4 in 3 1/2 hours, which marked the longest match in this tournament's history.

The Polish Radwanska will face the third-seeded former world No. 1 Williams (3-0) on Saturday in a rematch of the Wimbledon final, which was won by the powerful American. Williams is 3-0 lifetime against Radwanska.

In addition to Azarenka, Williams and Li, this week's Red Group, which was won by Williams, also featured fifth-seeded German Angelique Kerber, who went 0-3 in her round-robin activity.

Saturday's semifinal winners will meet in the lucrative final on Sunday. If Sharapova or Williams title this week, one of them would claim $1.75 million as an undefeated champion.

The sizzling-hot Williams has won 46 of her last 48 matches overall and is a perfect 12-0 against top-five players this season.

The 31-year-old star is the reigning Wimbledon, U.S. Open and Olympic champion and captured WTA Championships titles in 2001 and 2009 and is a two-time runner-up at this event.