Gael Monfils of France returns a shot during the ATP Cup Group A match against Novak Djokovic of Serbia in Brisbane, Australia, on Jan. 6, 2020. (Photos: Xinhua)

Gael Monfils of France returns a shot during the ATP Cup Group A match against Novak Djokovic of Serbia in Brisbane, Australia, on Jan. 6, 2020.

Gael Monfils of France reacts during the ATP Cup Group A match against Novak Djokovic of Serbia in Brisbane, Australia, on Jan. 6, 2020.

Novak Djokovic of Serbia returns a shot during the ATP Cup Group A match against Gael Monfils of France in Brisbane, Australia, on Jan. 6, 2020.

Novak Djokovic of Serbia returns a shot during the ATP Cup Group A match against Gael Monfils of France in Brisbane, Australia, on Jan. 6, 2020.