NEW YORK • Their rivalry has taken an envious route, skipping from Argentina up to Monaco before flitting about Spain, France and Italy for seven matches in 13 months.

It has included brief two-set bouts and rugged three-setters, with seven wins for the "King of Clay," and an admirable three victories for his presumed successor.

But for all their history, Rafael Nadal and Dominic Thiem have never played on a hard court, and they have never played in New York.

Today, they will try it for the first time in the US Open quarter-finals at the Billie Jean King National Tennis Centre and see how it goes.

"On clay, it's one of the biggest challenges in sport to beat or compete with this guy (Nadal)," Thiem said. "I hope that it's a little bit more comfortable on hard court, but I'm not sure."

It would do him well to cling on to that thought.

The change of scenery might even be good for the Austrian, who turned 25 yesterday and defeated Wimbledon finalist Kevin Anderson 7-5, 6-2, 7-6 (7-2) on Sunday in a match so dominant that he lost only four points on his first serve.

The last time the burgeoning rivals met was in the French Open final, when Nadal beat Thiem in straight sets to claim his 11th title in Paris in early June.

But the world No. 1 is more vulnerable at Flushing Meadows than he is at Roland Garros. At the French Open, he has an 86-2 career record.

At the US Open, however, he is a more modest 53-10 and has won it only three times.

The 32-year-old has certainly been pushed in his last two matches, both of which have gone to four sets. He followed a thrilling upset bid from Russia's Karen Khachanov in the third round with a 6-3, 6-3, 6-7 (8-6), 6-4 win over Georgian Nikoloz Basilashvili in the fourth round on Sunday.

"Two matches in a row, very tough ones," the Spaniard told reporters afterwards, understating his nearly eight hours of work.

His toiling was fruitful, however - this is the first year Nadal has made it to at least the last eight of every Grand Slam since 2011.

Thiem has been tested too, requiring nine combined sets to defeat unseeded Americans Taylor Fritz and Steve Johnson en route to the fourth round.

But this generally is also not his best season - the best time to watch Thiem is on red clay in spring. He owns 10 career ATP Tour titles, eight of which have come on clay, two Grand Slam semi-final appearances and one final appearance, all three of which have been at Roland Garros.

It is no wonder why the tennis world assumes that as far as clay is concerned, Thiem is Nadal's heir apparent even if he is not totally comfortable in the role.

"I grew up on the clay, so I think it's natural that I feel most comfortable on this surface, but I like the hard court," he added.

Although this is Thiem's first quarter-final appearance in a Major that is not the French Open, for Nadal, the surface hardly matters and he is expecting a stiff challenge from the world No. 9.

The top seed cited Thiem's powerful, disciplined groundstrokes, which can do damage across multiple surfaces and said: "It's a different kind of match than clay, but it's still a tennis match. I know how he plays. He knows how I am playing.

"It's going to be interesting one, tough one, hopefully for both of us. And hopefully, who will play better, will have better chance."

Joining Nadal and Thiem in the quarter-finals will be 2009 US Open champion Juan Martin del Potro, after the Argentinian beat Croatia's Borna Coric 6-4, 6-3, 6-1.

Third-seeded del Potro will take on American John Isner, who edged past Canadian Milos Raonic in a battle of big servers 3-6, 6-3, 6-4, 3-6, 6-2, for a semi-final berth today.

AGENCE FRANCE-PRESSE, WASHINGTON POST

US OPEN

Day 9: Singtel TV Ch114 & StarHub Ch208, 11.30pm