But Russian eighth seed Ekaterina Makarova lost to Slovakian Magdalena Rybarikova, 6-2, 7-5.
The seven men from the United States represent the country’s smallest group at the All England Club since there were five in 1947.
Romanian third seed Simona Halep plays Slovakian Jana Cepelova later, and Danish fifth seed Caroline Wozniacki takes on China’s Saisai Zheng.
Andy Murray didn’t disappoint his local fans on Tuesday.
Petra Kvitova probably wishes she could be this nervous before every match if her 35-minute 6-1 6-0 rout of Dutchwoman Kiki Bertens at Wimbledon on Tuesday was anything to go by.
That drew an incredulous look and a chuckle from the tournament’s 2013 champion.
The 21-year-old from Montreal, ranked 12th, suffered an abdominal injury last week and her loss to world number 117 Duan is her 12th defeat in 14 matches. “I don’t pretend to be any different just because I win tennis matches, so hopefully brands appreciate my approach and my likeability, because it’s who I am”.
Mikhail Youzhny lost Tuesday to France’s Benoit Paire 6-4, 6-4, 6-3.
When Serena was asked about that possibility, she said she didn’t know there could be an all-Williams match in the round of 16. “I’m really glad with how I played”. “It depends on how they deal with it. I took the time off and I’m happy I did it”.
No immediate reason was given for the withdrawal, although both sisters are still involved in the singles tournament and could meet in the fourth round.
Not for Petra Kvitova any thoughts of easing her way into the defence of her title.
The only point Kvitova lost on serve came when she double-faulted on the first point of the final game, hitting a 93 miles per hour (150 kph) second serve just wide. On her best form the German is a match for almost anybody, but there is still a major question about her ability to handle the big occasion mentally.
Breakfast at Wimbledon? How about a double bagel?
The 10th seed, who won the Aegon Classic in Birmingham earlier this month, replicated the wins Venus Williams and Andrea Petkovic secured on Monday.
Sports marketing experts were predicting, as she reached the Wimbledon final, that Bouchard would go on to surpass Maria Sharapova as the richest female athlete in the world.
After the hottest day on record in Wimbledon history on Wednesday, temperatures were cooler and a light drizzle forced a 45-minute delay to the start of play on the outside courts.
National Hockey League star Henrik Lundqvist is among the guests invited to the Royal Box on Centre Court.
What then, would Kvitova make of London or New York? Federer beat Damir Dzumhur 6-1, 6-3, 6-3.