Eleventh seed Schwartzman looked to be heading home when he trailed Kevin Anderson 6-1 6-2, but an incredible turnaround saw the Argentine through to his second grand slam quarter-final appearance.

There he will face reigning champion Nadal, whose bid for an 11th Roland Garros title sauntered on with a straight-sets win against the spirited Maximilian Marterer.

Juan Martin del Potro and Marin Cilic are also through, with four of the top five seeds in an exciting last-eight line-up.

Schwartzman considered his match against 6ft 8in Anderson a David-versus-Goliath challenge and an awful start put the South African in complete control.

The world number 12 came roaring back, though, winning the final three sets 7-5 7-6 (7-0) 6-2, before collapsing in a heap as he tried to take in the magnitude of his comeback.

Schwartzman then asked reporters: "Did you read David and Goliath? That's why [he kept believing]. That's why.

"I read it when I was young, in school, and I just try to think of that when I see Kevin or the guys who are two metres [tall]."

Nadal had too much for Marterer on Court Philippe Chatrier, with a 6-3 6-2 7-6 (7-4) win the 900th of his career - the Spaniard becoming the fifth man to reach that total.

A large chunk of those successes have come on clay, with Nadal pointing out that his fine record at this time of the year extends beyond Roland Garros.

"I never like to be arrogant at all but, being honest, I won 11 Monte-Carlos, 11 Barcelonas, eight Romes," he said. "It's about the surface, not only the place."

The Spaniard did then clarify, though, with a smile: "It is not true that I was born on clay!"

Nadal was asked in his post-match news conference about a potential semi-final meeting with John Isner, but such questions were premature as the giant American then crashed out to Del Potro in straight sets.

The fifth seed progressed 6-4 6-4 6-4, enjoying an easier afternoon than his next opponent, Cilic, who played out a five-set thriller with Fabio Fognini.

Fognini appeared to be down and out as he hobbled through the second set - falling two behind - and his mood was as stormy as the weather forecast when he repeatedly drew jeers from the crowd for smashing his racket in frustration.

The Italian was cheerier after winning the next two sets and directed heart-shaped hand signals towards the stands following another outburst, but a scintillating fifth went in Cilic's favour.