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.
The world number one will 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 seed 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.
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.