Rafael Nadal kept his US Open campaign on track on Sunday despite a painful knee as Spanish-speaking claycourters clamped a stranglehold on the bottom half of the draw.
The 21-year-old second-seeded Spaniard charged into the last 16 by defeating big-hitting Frenchman Jo-Wilfried Tsonga 7-6 (7/3), 6-2, 6-1, winning 10 out of the last 11 games after a tough first set.
Following him into the fourth round were compatriots and close friends Carlos Moya and David Ferrer as well as Argentine pair Juan Monaco and Juan Ignacio Chela, all better know for their skills on clay rather than hardcourts.
American hopes of posting a third qualifier for the last 16 after Andy Roddick and James Blake were sunk when Robby Ginepri went down 5-7, 6-4, 4-6, 6-4, 6-3 to Switzerland's other top-100 player, Stanislas Wawrinka.
French Open champion Nadal once again had strapping on both knees when he took on Tsonga, but he looked much more at ease than in the first two rounds when he struggled with his fitness and needed courtside treatment.
Things were improving, he said, but Nadal admitted that the pain was still a factor he had to deal with.
"When I go on court, I start with a little bit pain, but after it is not so bad. The knee gets a little bit warmer," he said.
"When I get in tie-break, I don't think about the pain for a moment."
His next opponent will be compatriot and close friend Ferrer, who saved a match point against Argentina's David Nalbandian before winning a gruelling 6-3, 3-6, 4-6, 7/6 (7/5), 7-5 encounter that lasted just short of four hours.
Nalbandian, the last man to beat Roger Federer in the US Open when he won through to the semifinals in 2003, had his match point at 5-4 in the fifth but he slapped a easy-looking backhand drive into the net.
Ferrer made him pay a heavy price for that miss as he held serve and then won the next two games to go through to the US Open fourth round for the first time.
Asked how he would tackle the challenge of Nadal, Ferrer replied, "He's an unbelievable player."
"He plays at a great level, he runs all the time and it's difficult to win against him. But I will just have to do my best things and enjoy it."
Also winning a marathon was Chela, one of a record five Argentinians playing their third-round ties in the bottom half of the draw on Sunday. He finished stronger to beat Croatia's Ivan Ljubicic 6-4, 6-7 (5/7), 2-6, 6-3, 6-3.
The 28-year-old Chela has long played in the shadow of more illustrious compatriots, but his mixture of experience, resolve and fitness proved too much in the end for Ljubicic, who reached a career-best third in the world rankings last year.
The big Croatian was in command early on, but he was gradually worn down by the relentless baseline application of the South American.
Life was much simpler for the fast-rising Monaco, who trounced Lleyton Hewitt's conquerer Agustin Calleri and will next go up against third seed Novak Djokovic of Serbia, who had a routine 6-1, 6-3, 6-4 win over 18-year-old Juan Martin del Potro of Argentina in the featured night match on the Arthur Ashe Stadium court.
"Playing in the biggest court in tennis and as third seed it was hard to remain calm and focussed on my game," the Serb said.
Moya, at 31 playing in his 12th US Open, reached the fourth round for the fourth time with a gritty four-hour 4-6, 7-5, 7-6 (7/5), 4-6, 6-4 win over Germany's Philipp Kohlschreiber.
He will have the chance to avenge compatriot and eighth seed Tommy Robredo, who was upset 6-1, 6-3, 6-2 by Ernests Gulbis, a 19-year-old Latvian newcomer whose grandfather played basketball for the old Soviet Union.