Ivanovic dumped out in US
Ana Ivanovic became the second top-10 player to crash out of the US Open as she suffered a second-round exit at the hands of Czech Karolina Pliskova.
After fourth seed Agnieszka Radwanska went down early on Wednesday, it was Ivanovic's turn to suffer the early shock on Thursday.
The eighth seed went into the tournament with high hopes of marking her best season since she won the French Open in 2008 with a good run in New York.
But she found world No 42 Pliskova in fine form and succumbed to a 7-5 6-4 defeat, with the 22-year-old reaching the third round at a grand slam for the first time in her career.
For all her success this year, winning three titles, deep runs at slams have continued to elude Ivanovic.
The exception was the Australian Open, where she defeated Serena Williams to reach the quarter-finals, but she then went on to lose in the third round at both the French Open and Wimbledon.
Top seed Williams had no such problems, needing just 56 minutes to see off fellow American Vania King 6-1 6-0.
Williams, bidding for a hat-trick of US Open titles and sixth in total this year, will play another compatriot, Varvara Lepchenko in the third round.
"It's so hard to play in the wind," Williams said of the blustery conditions at Arthur Ashe Stadium.
"Especially one side's a little harder, it makes your serve different. Getting through that game was really important. You have to be able to adjust."
Victoria Azarenka, beaten by Williams in the final at Flushing Meadows in each of the last two years, won 12 of the last 14 games in a 6-3 6-2 victory over American Christina McHale.
Azarenka has had a nightmare season with injury and is seeded only 16th this time. The Belarussian needed three sets to battle past Misaki Doi in round one and lost the first three games to McHale before recovering in impressive fashion.
Opening round sensation CiCi Bellis saw her fairytale come to an end as the 15-year-old American was beaten 6-3 0-6 6-2 by Kazakh player Zarina Diyas.
In front of vociferous home support on Court 17 Bellis, who stunned Australian Open finalist Dominika Cibulkova on Tuesday, produced a stirring performance to bagel her opponent in the second set before fading in the decider.
Eugenie Bouchard, the No 7 seed, held off a stirring fightback from Sorana Cirstea to record a 6-2 6-7 (7-4) 6-4 victory, while 11th seed Flavia Pennetta, a semi-finalist last year, made smooth progress with a 6-4 6-3 victory over American Shelby Rogers.
But 2011 champion Sam Stosur wasted two match points on the way to a 3-6 6-3 7-6 (10/8) defeat to Estonia's Kaia Kanepi, while American Madison Keys, the 27th seed, went down 7-6 (7/4) 2-6 7-5 against Serbia's Aleksandra Krusnic in a match lasting two hours and 17 minutes.