BEIJING (REUTERS) - Novak Djokovic kept his juggernaut rolling at the China Open by improving to 26-0 with a 6-2 6-1 win over local hope Zhang Ze on Thursday which tied him with Jimmy Connors for the second-longest unbeaten record at an ATP Tour event.
The Serbian top seed, a five-time winner at the China Open, is now only behind Rafa Nadal who had a 31-0 run in the French Open at Roland Garros.
The world No. 1 was unable to identify any particular reason for his performance at the tournament and said the conditions here were just in sync with his game.
"The conditions are definitely suitable to my game," said Djokovic. "I feel very pleasant playing on the centre court. I guess as I keep coming back each year with that positive record, obviously it gives me more confidence knowing that I played so well in the past on this court.
"I just keep on going. That's all. There is no particular reason. There are a few things that play in my favour."
Next up for Djokovic in the quarter-finals will be American John Isner, who snatched victory from the jaws of defeat against Australian qualifier John Millman.
The Australian was serving for the match at 6-5 in the second set but Isner broke back then won the tiebreak and then the deciding set for a 4-6 7-6(5) 6-4 win.
In other men's matches, Fabio Fognini reached the last eight after a 6-2 2-6 6-2 win against number seven seed David Goffin while Pablo Cuevas of Uruguay beat Ivo Karlovic 7-6(5) 7-6(7).
In the women's draw, Spanish rising star Garbine Muguruza made her 22nd birthday one to remember by sealing her spot for the WTA Finals in Singapore with a nervous 1-6 6-2 6-1 win over Mirjana Lucic-Baroni.
"I was really nervous before the match, because I knew I could get to Singapore and it was also my birthday," the 2015 Wimbledon finalist said.
But US Open champion Flavia Pennetta had her hopes of qualifying for the season-ending tournament in Singapore dented when she lost 3-6 6-4 6-3 to Anastasia Pavlyuchenkova.
Pennetta, who is engaged to Fognini, has already announced her decision to retire at the end of the season.
Her compatriot and opponent in the US Open final, Roberta Vinci, also went out with a 6-1 3-6 6-2 defeat to American qualifier Bethanie Mattek-Sands.
Pavlyuchenkova's opponent in the quarter-finals will be Ana Ivanovic who edged out Svetlana Kuznetsova 7-5 4-6 6-2 in a thrilling battle.