Novak Djokovic is on course to defend his Shanghai Masters title after beating John Isner 7-5 6-3 to reach the quarter-finals.

Djokovic, who won the Japan Open last week, maintained his fine form after a straight-sets win against Denis Shapovalov in the previous round to dispatch big-serving 16th seed Isner in 75 minutes.

“It’s always a big challenge returning the serve,” Djokovic said.

“He’s got one of the biggest serves of all time.”

The world No.1 will now play Stefanos Tsitsipas in the last eight after the sixth-seeded Greek overcame Poland’s Hubert Hurkacz 7-5 3-6 7-6 (5).

Second seeded Roger Federer saved five set points in the opening set against Belgium’s David Goffin on his way to a 7-6 (7) 6-4 victory.

The 38-year-old Swiss now faces Alexander Zverev after the German came through 6-0 7-6 (4) against Russian opponent Andrey Rublev.

“I never really felt like I had the upper hand over David today,” Federer said.

“I thought he took really a lot of good decisions, and he was super fast on his feet today, which I think made it really hard for me to get my freebies and winners off the baseline.”

Daniil Medvedev extended his ATP Tour-leading number of wins this season to 56 but was pushed hard by Canadian qualifier Vasek Pospisil in a 7-6 (7) 7-5 victory.

Third seed Medvedev will play Fabio Fognini in the quarter-finals after the Italian 10th seed, who knocked out Andy Murray in the second round, defeated seventh seed Karen Khachanov from Russia 6-3 7-5.

Italy’s Matteo Berrettini faces Dominic Thiem after beating Spain’s Roberto Bautista Agut 7-6 (5) 6-4. Fourth-seeded Austrian Thiem defeated Georgia’s Nikoloz Basilashvili 6-3 6-4.