The Serbian is into the last four on the hard courts of New York despite completing just two of his five matches, against Poland's Jerzy Janowicz in round one and Britain's Kyle Edmund in round four.

Czech opponent Jiří Veselý withdrew before his round two clash to hand Djokovic a walkover, before Russia's Mikhail Youzhny pulled out injured in round three with the Serbian 4-2 up in the first set.

Djokovic's quarter-final with Frenchman Jo-Wilfried Tsonga lasted just two sets today as his opponent retired with a knee problem while 6-3, 6-2 down.

The 12-time Grand Slam winner's good fortune is omnious news for his rivals as he will presumably be fresher for the semi-finals and final.

The 29-year-old went into the tournament with ankle problems of his own as well as a dip in form, which resulted in surprise early exits at both Wimbledon and the Olympics in Rio.

"This was the scenario that I needed and I wished for," said the world number one.

"I got a lot of days off and recovered my body.

"Right now I'm feeling very close to the peak. 

"That's the position where I want to be."

Djokovic will face another Frenchman, Gaël Monfils, in the last four, after he beat his compatriot Lucas Pouille 6-4, 6-3, 6-3.

Pouille memorably knocked out Spaniard Rafael Nadal in five sets in round four but could not reach those standards again.

Britain's Olympic champion Andy Murray will play Kei Nishikori of Japan in their quarter-final today, with the other last eight clash featuring Switzerland's Stan Wawrinka and Juan Martin del Potro of Argentina.

In the women's competition, Denmark's Caroline Wozniacki breezed through to the last four by beating Latvia's Anastasija Sevastova 6-0, 6-2.

German second seed Angelique Kerber ended the hopes of last year's runner-up Roberta Vinci, beating the Italian 7-5, 6-0.

Ana Konjuh of Croatia will meet Karolína Plíšková of the Czech Republic in the quarter-finals today, with American ace Serena Williams colliding with Romania's Simona Halep.