Safarova sent packing

Lucie Safarova joined the US Open seeds casualty list on Tuesday when the Czech left-hander became the fourth top-10 player to lose in the first round.

Sixth-seeded Safarova slipped to a 6-4, 6-1 defeat to Ukraine's Lesia Tsurenko, the woman she defeated in the semifinals in New Haven just last week.

With world number three Maria Sharapova having pulled out of the tournament through injury, Safarova's defeat also served to ease Serena Williams's path to a calender Grand Slam.

World number two Simona Halep avoided the upsets when she reached the second round thanks to New Zealand opponent Marina Erakovic retiring with a knee injury.

Halep was leading 6-2, 3-0 when her 99th-ranked rival called it quits, having received a medical timeout for treatment on her right knee at the end of the first set.

Romanian 23-year-old Halep goes on to face either Kateryna Bondarenko of Ukraine or Yulia Putintseva of Kazakhstan for a place in the last 32.

Another winner on Tuesday was German 11th seed Angelique Kerber, a 2011 semi-finalist, who saw off Romania's Alexandra Dulgheru 6-3, 6-1.

Earlier, two-time champion Rafael Nadal survived a scare at the hands of Croatian teenager Borna Coric to reach second round.

Nadal prevailed 6-3, 6-2, 4-6, 6-4 against his 18-year-old opponent.

Three-time defending champion Serena Williams launched her quest for a historic title Monday by overwhelming 86th-ranked Russian Vitalia Diatchenko and advancing to the second round.

The world number one was a 6-0, 2-0 winner after only 30 minutes.

Top-ranked Novak Djokovic also cruised into the second round on the men's side but Japanese fourth seed Kei Nishikori crashed out after his US Open runner-up effort last year.

Djokovic needed only one hour and 11 minutes to capture a 6-1, 6-1, 6-1 victory over Brazil's Joao Souza.