Two-time Grand Slam champion Li Na is out of next month's US Open because of a knee injury.
The 2014 US Open will take place from 25 August to 7 September. Serena Williams won her 17th Grand Slam title by beating Azarenka at Flushing Meadows last year. For information visit the official US Open site.
Tomas Berdych lived up to his billing in the second round of the Citi Open in Washington with a win over Robby Ginepri.
Serena Williams made a winning return to action by beating Karolina Pliskova at the Bank of the West Classic.
Marina Erakovic safely made it through to the third round of the Citi Open with a comfortable win over Shelby Rogers.
Rafael Nadal's US Open participation is in doubt after pulling out of the next two ATP Masters events due to injury.
Lukas Rosol safely made it through to the quarter-finals of the bet-at-home Cup Kitzbuhel on Wednesday.
Sabine Lisicki recorded the fastest ever serve in WTA history during her first-round match in Stanford.
British number one Heather Watson suffered a first-round exit at the Citi Open in Washington DC on Tuesday.
Kevin Anderson became the first man through to the third round of the Citi Open on Tuesday.
Sixth seed Robin Haase suffered a shock first-round defeat to Paolo Lorenzi at the bet-at-home Cup in Kitzbuhel.