World No 1 Rafael Nadal wasted no time booking his place in the third round, steamrolling Ryler DeHeart while women's top seed Ana Ivanovic became the biggest casualty of the US Open.
French qualifier Julie Coin scored one of the most shocking upsets in Grand Slam history Thursday, sending world No 1 Ivanovic crashing out in the second round.
Coin, who is ranked 188th in the world, was making her Grand Slam debut after successfully coming through the qualifying rounds.
She had tried but failed earlier this year to qualify for the other three Grand Slams -- Australian Open, French Open and Wimbledon.
The 25-year-old Coin clinched the 6-3, 4-6, 6-3 win on her third match point in the one hour, 57 minute match at the main Arthur Ashe Stadium.
"Today I felt nervous at the beginning and then it went away," said Coin. "I don't know how I did it.
"I am not thinking about anything right now. Just enjoying the moment."
Ivanovic looked like the more nervous of the two in the deciding third set. She posted a total of eight double faults and made 37 unforced errors to 26 for Coin.
"This is very disappointing to me but something I have to accept," Ivanovic said. "I never saw her (Coin) play before.
"She played a lot better than I expected. She served very well."
Coin moves through to the next round where she will play countrywoman Amelie Mauresmo.
Ivanovic has not had a long reign at number one. Her stay at the top was interrupted for a week earlier this month, but she since regained the top spot in the WTA rankings.
Nadal ripped returns on serves, laced passing shots, and crafted crisp volleys in a dynamic performance to beat DeHeart 6-1, 6-2, 6-4 in the second round.
"I did well. I had to come back in third set from down 3-0 in games so I am happy with the victory," Nadal said.
"I am happy to be in the third round, for me this is a very important tournament."
Nadal, who has won eight titles this season including his fourth French Open crown and first Wimbledon trophy, has never made it past the quarter-finals at the US Open and hasn't made it to a hardcourt Grand Slam final.
But he looks poised to make a run this week as he smacked 21 forehand winners and made just 11 unforced errors in the one hour, 40 minute night session match on the Arthur Ashe Stadium court.
The 22-year-old Nadal became the first Spanish tennis player to win an Olympic gold medal at the Beijing Games.
He officially became the new world number one on August 18, ending Roger Federer's record run of 237 weeks top the ATP rankings.
Top seed Nadal advances to the third round where he will play Viktor Troicki of Serbia.
"He is a good player. I am going to have to play better to beat him," Nadal said.
Serena and Venus Williams rolled over their opponents on Thursday with Serena defeating Elena Vesnina of Russia 6-1, 6-1 and Venus brushing aside 113th ranked Rossana De Los Rios 6-0, 6-3.
Serena needed just 58 minutes to dispatch Vesnina who is ranked 71st in world.
Asked if she would have preferred a more competitive match, Serena said she likes to get them over quick.
"Not too many long rallies but I am serving well," said the fourth seeded Serena.
The seventh-seeded Venus moves through to the third round where she will play Alona Bondarenko who beat Sabine Lisicki 6-4, 1-6, 6-4.
Serena next faces Japanese veteran Ai Sugiyama.
"She's pretty much relentless," said Serena of Sugiyama. "I better be ready. That girl is a tough cookie."
Sugiyama rallied to beat Olga Govortsova of Belarus 4-6, 7-6 (7/4), 6-1.
The Japanese men were also celebrating Thursday as Kei Nishikori advanced to the third round when Roko Karanusic, of Croatia, retired at the end of the second set with the Japanese teen leading 6-1, 7-5.
Nishikori, who is playing in his first US Open, will face fourth seed David Ferrer, of Spain.
"I tried to go to the net more often, because he was using the slice a lot," Nishikori said.