Del Potro said he felt very sorry for Nadal. He said: "It's not the best way to win a match. I love to play against Rafa because he's the biggest fighter in this sport and I don't like to see him suffering."

"I didn't expect to get to another Grand Slam final in my favorite tournament. I had my biggest memories on this court in 2009 when I beat Nadal in semifinals and Roger Federer in the final. I was a kid then, now I am much older," he added.

In the other semifinal, Nishikori gave all out and was able to make some sizzling shots from baseline, but he still came short in front of the awe-inspiring Djokovic.

Djokovic missed the tournament last year because of an injured right elbow that eventually required surgery. But he is back to his best in time as he bids for his third title at Flushing Meadows and 14th Grand Slam title overall.

Earlier, third-seeded Americans Mike Bryan and Jack Sock defeated No. 7 seeds Lukasz Kubot of Poland and Marcelo Melo of Brazil 6-3, 6-1 in just 74 minutes to win the U.S. Open, giving Bryan his all-time men's doubles record 18th Grand Slam crown.

At 40 years, 4 months, he also passed Indian star Leander Paes as the oldest Grand Slam champion in the men's doubles.

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