US Open Tennis 2012: Watch Live Stream Online of Sharapova vs. Azarenka, Williams vs. Errani; Prediction, Preview

When and where: Play gets underway on Arthur Ashe Stadium at noon ET with the men's doubles final, followed by the two women's semifinals. Coverage will be provided by CBS, with a live stream available on USOpen.org.

Preview: It promises to be a titanic tussle as Maria Sharapova and Victoria Azarenka face off in Friday's first semifinal at Flushing Meadows. The two powerful hitters have developed quite the rivalry, meeting three times this year alone.

Their highest-profile match to date saw Azarenka claim her maiden Grand Slam title with a crushing straight-sets victory over Sharapova back in January. While their head-to-head series is closely matched at 5-4 in Azarenka's failure, notably the Belarusian has won the last four meetings on hard courts.

While before the final in Melbourne Azarenka was still seen as the player on the rise against the established power of Sharapova, the 23-year-old has enjoyed an incredibly consistent year to see her ranked at the top of the women's game.

Azarenka's progress at this year's US Open had been remarkably smooth before running into Samantha Stosur in the quarter finals. In defeating the defending champion in a final set tie break the Arizona resident showed she has the toughness required at the key moments. Incredibly that improved Azarenka's three-set record for the season to 11-0.

As if evidence was needed at the resilience of both competitors, Azarenka's record in matches that go the distance is bettered by that of Sharapova, who is 12-0.

Almost incomprehensibly for two of the game's leading players, this is Azarenka's first time past the fourth round in New York, while Sharapova is enjoying her first run past the round of 16 since claiming the title in 2006.

As always Sharapova's serve will be crucial to her chances. Arguably one of the main reasons she has struggled at Flushing Meadows since her return from shoulder surgery is the fact that Arthur Ashe Stadium is widely known as the windiest court in all of tennis. The Russian's 11 double faults in her three-set win over Marion Bartoli in the quarterfinals highlight that the problem still remains.

If Sharapova can't dictate on her service games then Azarenka will have too much power and will crucially be able to dictate from the back of the court.

On paper, the day's second semifinal promises to be a much more one-sided affair. Serena Williams, fresh from victory at Wimbledon and the Olympic Games, meets first time Flushing Meadows semifinalist Sara Errani.

Williams has continued her sensational summer form in New York. The 30-year-old has yet to drop a set so far and remarkably has breezed through her five matches for the loss of just 16 games. Integral to her recent run has been some phenomenal serving that has given her the platform to dominate her opponents.

Serving is certainly not the strong point of Italian Errani, who may struggle merely to get a foothold in the match. The 25-year-old has enjoyed a stunning season, already having reached the final at Roland Garros. When the new rankings come out she will be safely ensconced in the world's top 10, not to mention rising to the N0.1 player in the world in doubles.

But if Williams has merely a solid day, she will have far too much for Errani.