NEW YORK Brief biographies of the women's semi-finalists at the 2011 U.S. Open (prefix number denotes seeding):
1-Victoria Azarenka (Belarus)
Grand Slam titles: 1 (Australian Open 2012)
Won her maiden grand slam title at the Australian Open in January to move to the top of the world rankings for the first time as she started the season with a 26-match winning streak. Has won three other titles this year and a gold medal in mixed doubles at the London Olympics. Won the U.S. Open as junior in 2005 and is making her first appearance in the semis in the main event. Cruised through her first four matches in straight sets then survived a comeback from defending champion Sam Stosur in the quarter-finals before winning a third set tiebreaker.
3-Maria Sharapova (Russia)
Grand Slam titles: 4 (Australian Open 2008; French Open 2012; Wimbledon 2004; U.S. Open 2006)
Appearing in her first U.S. Open semi-final since winning the title six years ago as a teenager. She won the French Open in June to become just the 10th woman to win all four grand slam singles titles. Won tournaments in Stuttgart and Rome earlier this year and was a finalist at the Australian Open and London Olympics. Won her last two matches in three sets and has not lost any match this year that has gone the distance.
4-Serena Williams (U.S.)
Grand Slam titles: 14 (Australian Open 2003, 2005, 2007, 2009, 2010; French Open 2002; Wimbledon 2002, 2003, 2009, 2010, 2012; U.S. Open 1999, 2002, 2008)
The greatest player of her generation, chasing her fourth U.S. Open title. Suffered a surprise defeat in last year's final to Australia's Sam Stosur but has been in great form in the past few months. She won her fifth Wimbledon title in July then the singles and doubles gold medals at the London Olympics. She is the only woman through to the semi-finals without dropping a set and is bidding to become the oldest woman to win the U.S. Open title since Margaret Court won aged 31 in 1973.
10-Sara Errani (Italy)
Grand Slam titles: 0
Made her first grand slam singles final at this year's French Open. Teamed up with her countrywoman Roberta Vinci to win the doubles title at Roland Garros. The pair are also through to Sunday's U.S. Open doubles final and Errani will become the number one doubles player in the world when the new rankings are released on Monday. Enjoying the best season of her career, Errani has won four titles and made her first U.S. Open semi but suffered an embarrassing moment at Wimbledon when she failed to win a single point in her "golden set" loss to Yaroslava Shvedova.
(Compiled by Julian Linden; Editing by)