Rafael Nadal plays his quarterfinal match at the US Open against Diego Schwartzman in New York City on Wednesday. Photo: IC

Rafael Nadal said he felt "in good shape" after advancing to the semifinals of the US Open with a battling 6-4, 7-5, 6-2 win over Argentine 20th seed Diego Schwartzman.

Second seed Nadal, a three-time champion in New York, will play Italy's Matteo Berrettini for a berth in the final after the 18-time Grand Slam winner overcame a gritty performance from the 1.70-meter Schwartzman.

The Spaniard needed the best part of three hours to record an eighth straight win over two-time US Open quarterfinalist Schwartzman in a match that finished early Thursday morning.

He received treatment to his left forearm early in the third set but swiftly allayed any injury fears, after a knee injury forced him to retire during last year's semifinal against Juan Martin del Potro.

"I'm feeling good. Today was very humid day, very heavy day. I had some cramps in the end of the second and first five games, six games of the third. And then I take some salt, that's all, and then was over," Nadal said.

"The body is in good shape, I think. No big problems. Just of course now a little bit tired, long day, 1:30 [am]. Need to go to sleep. But I really believe that I'm going to be in good shape."

Nadal rolled through the first three rounds untested, a run that included a second-round walkover, but the 33-year-old feels stiffer competition in his past two matches - against Marin Cilic and Schwartzman - has left him primed for another shot at the US Open title.

"Today I make a step forward, in my opinion. That match give me confidence. Two matches in a row against two tough opponents. That's a moment to increase a little bit more the level, and I really believe that I can do it," Nadal said.

The win over Schwartzman sent Nadal through to a 33rd Grand Slam semifinal - third most in history ­behind Roger Federer (45) and ­Novak Djokovic (36) - as he reached the last four in New York for the eighth time.

Nadal is the only former major champion left in the men's field following the elimination of ­Federer and Djokovic, leaving him as the clear frontrunner in his pursuit of a 19th major title.