Rafael Nadal hits the ball against Ryan Harrison during their...

Rafael Nadal hits the ball against Ryan Harrison during their 2013 U.S. Open men's singles match at the USTA Billie Jean King National Tennis Center. (Aug. 26, 2013) Credit: Getty Images

Standard Grand Slam tennis procedure: No. 2 U.S. Open seed Rafael Nadal rolled on Saturday. His 6-4, 6-3, 6-3 win over Croatia's Ivan Dodig, ranked 38th in the world, powered Nadal into the fourth round, and he not only has not lost a set but has yet to have his serve broken in the tournament.

"Will happen," he assured. "No worries."

Whether he actually will lose a match is another matter. Nadal already has won nine tournaments this year, including, of course, his record eighth French Open title. His play on hardcourts -- taking titles in Montreal and Mason, Ohio, this summer -- has belied previous worries that his chronic knee problems are a detriment on the surface.

And, as is his habit, he cautioned against overanalyzing his good run.

"It's always the same thing," he said. "When somebody is having success, we find reasons that's why he's having success. I'm having success today because I am playing well. That's all.

"I didn't change nothing in my life. I didn't change nothing in my practices. I tried to play mentally a little bit more aggressively. When you are playing well, you have the chance to play more aggressive. When playing bad and not feeling the ball very well, I am not that good to keep playing aggressive."

Next up for Nadal is No. 22 seed Philipp Kohlschreiber, who ousted the highest American seed, No. 13 John Isner, Saturday, then said it wasn't necessary to remind that Nadal "is in pretty good shape, winning almost every match on hardcourt."

Other according-to-form results: No. 7 Roger Federer defeated Adrian Mannarino of France, 6-3, 6-0, 6-2. No. 4 David Ferrer of Spain beat Kazakhstan's Mikhail Kukushkin, No. 8 Richard Gasquet of France beat No. 32 Dmitry Tursunov of Russia and Canada's Milos Raonic beat No. 23 Feliciano Lopez of Spain.

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