Novak Djokovic moved a step closer to retaining his Shanghai Masters title by beating Vasek Pospisil in straight sets to seal a place in the quarter-finals.

The top seed, winner of this tournament in three of the last four years, will face Mischa Zverev in the last eight after seeing off qualifier Pospisil 6-4 6-4 on Thursday.

Djokovic, playing his first tournament since losing to Stan Wawrinka in the US Open final last month, was dominant from the baseline and three breaks were sufficient to keep him on course for an eighth tour-level title this year.

The 12-time grand-slam champion raced into a 4-0 lead, but Pospisil hit back by reeling off three games in a row before the favourite halted his momentum and wrapped up the opening set.

Canadian Pospisil's crunching forehand and positivity at the net gave Djokovic plenty to think about, but the Serb claimed the only break of the second set in game seven and needed only one match point to advance after 81 minutes of action. 

Djokovic, who made only 15 unforced errors, has now won all four matches against Pospisil as he attempts to fend off the challenge of Andy Murray to finish the year at the top of the rankings.