Top seed Novak Djokovic extended his winning run at the China Open to 21-0 after straight sets win over Vasek Pospisil of Canada on Wednesday.
The defending champion, who is bidding for his fifth successive triumph in Beijing, won 20 points on his Pospisil serves and converted 4 of the 9 break points presented by his opponent to claim a a 6-3 7-5 win.
The 27-year-old Serb will face fifth seed Grigor Dimitrov or Pablo Andujar in the round of 16.
Djokovic has his sight on the year-end number one ranking for the third time in the last four years and will need to excel in China to boost his points.
“It’s definitely always the highest priority out there with winning Grand Slams,” he said.
“That gives me plenty of motivation. It would mean, of course, a lot to me. That ‘s why I’m out here in Beijing and (next week in) Shanghai, competing and trying to get that year-end number one.”
Play on all outside courts was suspended for the day, but eighth seed John Isner was not deterred from reaching another ace milestone on Centre Court.
The American saved a match point in a third set tie-breaker to beat Spain’s Tommy Robredo 3-6 7-5 7-6 (7-4).
Isner took his total aces count to 901 after the second round win over Robredo, the third straight year he has served 900 or more aces. The 29-year-old currently trails Ivo Karlovic, who has had 940 aces coming into the week, in the 2014 ATP MatchFacts.
The 29-year-old will play either Victor Troiki or Tomas Berdych in the quarter-finals.