Rafael Nadal of Spain returns a shot during his men's singles tennis match against Carlos Berlocq of Argentina at the Shanghai Masters tennis tournament, Oct 10, 2013. [Photo/Agencies]

Elsewhere, Nadal, who just reclaimed the No 1 spot from Djokovic, eased past the opening set against Argentine Carlos Berlocq at 6-1, but had to finally see the opponent off with a tense tiebreak in the second.

The Argentine led 5-2 after a mini-break, but Nadal held nerves to take five points in a row to demonstrate his supremacy.

His reward will be quarterfinal clash against Swiss Stanislas Wawrinka, who defeated Canadian Milos Raonic 7-6(2), 6-4.

Djokovic, the defending champion and top seed here, enjoyed a much easier time of it, prevailing with a 6-3, 6-3 victory over Italian Fabio Fognini. The Serbian master shall take on Monfils in the last eight fixtures.

Earlier in the day, Juan Martin del Potro advanced to the last eight without striking a ball when 35-year-old Tommy Haas withdrew due to a back injury.

The Argentine sixth seed will play Spaniard Nicolas Almagro.