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The world number one made light work of Hanfmann, who defeated Andy Murray the day before, after a 6-3 6-3 victory in Switzerland.

Serbia's Djokovic saved nine of the 10 break points faced and won six straight games in the second set for a routine victory, responding emphatically after going 3-0 down.

The winner of a last-16 meeting between Denis Shapovalov and Tallon Griekspoor awaits in the last eight for Djokovic, who triumphed with little trouble on his 37th birthday.