The world number one was due to face Serbian Filip Krajinović but pulled out of the contest before the players took to the court at the AccorHotels Arena.

Top seed Nadal, a winner of 16 Grand Slam titles, had his knee heavily strapped in a battling three-set win against Uruguay's Pablo Cuevas yesterday.

The injury has thrown his participation at the World Tour Finals at London's O2 Arena, scheduled to run from November 12 to 19, into doubt.

"For me it's not about London," Nadal said.

"For me it's about the longer term.

"And longer term, I'm going to do the treatment I believe that is going to be more safe and more important to keep playing tennis as long as possible."

Krajinović has progressed to the last four by virtue of Nadal's retirement.

The Serbian will go up against John Isner of the United States in the last four after the big-serving American beat Argentina's Juan Martin del Potro 6-4, 6-7, 6-4.

Julien Benneteau of France caused a quarter-final upset as he ousted third seed Marin Čilić of Croatia in straight sets.

Benneteau delighted the home crowd with a 7-6, 7-5 success over Čilić, who finished as runner-up at Wimbledon earlier this year.

The Frenchman will play American Jack Sock tomorrow after he came through a tough contest with Spain's Fernando Verdasco 6-7, 6-2, 6-3.

Julia Görges of Germany completed the last four line-up at the Women's Tennis Association Elite Trophy in Zhuhai as she ousted top seed Kristina Mladenovic of France.

Görges, the world number 18, needed to win one set to reach the next round and emerged with a 6-2, 7-6 victory at the Hengqin Tennis Centre.

US Open champion Sloane Stephens retired hurt when trailing 5-0 in the first set to Barbora Strýcová of the Czech Republic.

American Coco Vandeweghe, Australian Ashleigh Barty and Anastasija Sevastova of Latvia all booked their places in the last four yesterday.

Görges will play Sevastova, while Barty takes on Vandeweghe in the two semi-finals tomorrow, when action at the Paris Masters will also resume.