Andrei Rublev remained on course for a quarterfinal match against his teammate, who won the ATP Cup, Daniil Medvedev, with a 7-5, 6-2, 6-3 victory over 39-year-old Feliciano Lopez.
Last week, Rublev and Medvedev were undefeated in the ATP Cup with 12 teams to win the title for Russia.
Seventh-placed Rublev will face Casper Ruud of Norway in the fourth round.
Number 5 Stefanos Tsitsipas defeated Sweden’s Mikael Ymer 6-4, 6-1, 6-1 in the third round. It was a much straighter outing than his five-set marathon against Tanassi Kokinakis in the second round.