Serbia's 16-time Grand Slam champion, who won the Japan Open last week without dropping a set, cruised to a 6-3 6-3 second-round victory.

Defending champion Djokovic will play American John Isner next.

Isner hit 19 aces and lost only six points on his first serve in a 7-5 6-3 win over France's Lucas Pouille.

Austrian fourth seed Dominic Thiem, who won the China Open last week, beat Spain's Pablo Carreno Busta 7-6 (7-3) 6-3 to reach the third round in Shanghai for the first time.

Greek sixth seed Stefanos Tsitsipas edged out Canadian Felix-Auger Aliassime in a match between two of the most exciting talents on the men's tour.

Tsitsipas, who had never beaten his 19-year-old opponent, even on the junior circuit, had to be patient before securing a 7-6 (7-3) 7-6 (7-3) win.

Victory moved Tsitsipas closer to qualifying for the ATP Finals in London next month, while German fifth seed Alexander Zverev - another still hoping to qualify and have the chance to defend his title - also needed two tie-breaks to overcome French veteran Jeremy Chardy 7-6 (15-13) 7-6 (7-3).

Russian seventh seed Karen Khachanov, Spanish eighth seed Roberto Bautista Agut, Italian 11th seed Matteo Berrettini and Belgian 13th seed David Goffin progressed to boost their chances of reaching the season-ending finals.