World number one Roger Federer and Olympic champion Andy Murray face their first stern tests of the U.S. Open on Saturday after cruising through the early rounds.
Federer faces dangerous Spaniard Fernando Verdasco inside Arthur Ashe Stadium while Murray plays Verdasco's countryman Feliciano Lopez in Louis Armstrong Stadium.
Federer has not lost to Verdasco in four meetings but they have not played for three years and the 25th seed proved his capabilities this year with a win over 11-times major champion Rafa Nadal in Madrid.
Likewise, Murray is unbeaten in six starts against Lopez but the world number 31 is a streaky player who can trouble the elite.
Federer and Murray headline the day session at Flushing Meadows along with American Serena Williams, who will play unseeded Russian Ekaterina Makarova.
At night, Sloane Stephens, the teenage American, will start the prime time session in Arthur Ashe Stadium against 12th-seeded Serbian Ana Ivanovic before 16th-seeded Gilles Simon meets American Mardy Fish.
Federer said his five-set loss to Novak Djokovic in the semi-finals of the U.S. Open last year ended up being a blessing in disguise.
"I guess so, yes," he said.
"Not right after match point, not three weeks later, but I felt I played a great U.S. Open. I knew I was actually playing really good tennis.
"It was just not happening for me. Then the question is, can you maintain a good level of play without getting frustrated, wanting it too badly."
Federer broke through for his first major in more than two years when he claimed his seventh Wimbledon crown in July.
"I'm happy I had the right balance," he said. "I was able to just stay put and keep working hard and hope things were going to turn around for me.
"You have to make some tweaks. I remember sitting down and talking to everyone involved, trying to come up with improvements in the plan.
"Losing to Novak wasn't that unpleasant - it was the semi's."
Also in action on Saturday will be women's second seed Agnieszka Radwanska against former world number one Jelena Jankovic, American veteran James Blake against Canada's Milos Raonic and Blake's countryman Jack Sock against 11th-seeded Spaniard Nicolas Almagro.
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