Canadian Milos Raonic deafeated American Michael Russell 6-2, 7-5 to win his opening match at the SAP Open on Thursday in San Jose, California.
Roanic, the two-time defending champion and top-seeded player of the event, will play No. 6 Denis Istomin of Uzbekistan, who topped Germany's Benjamin Becker 6-3, 6-7 (5), 6-2.
Third-seeded Sam Querrey beat Lleyton Hewitt 7-6 (6), 1-6, 7-6 (4) on Thursday to reach the SAP Open quarterfinals.
Hewitt, the former top-ranked player in the world, double-faulted twice in the third-set tiebreaker, including match point. The Australian has 28 career titles, and beat Querrey in two previous meetings.
"A match like that, to grind through it, makes me feel pretty good," said Querrey. "It was a high quality match. He's a lot better than his ranking. A couple of double faults was all that separated us in the match."
Querrey's opponent in the last eight will be Colombia's Alejandro Falla, who reached his first quarterfinal of the season by knocking off seventh-seeded Marinko Matosevic of Australia 6-4, 6-4.
In other matches, Belgium's Xavier Malisse, seeded eighth, squeezed past Australia's Matthew Ebden 5-7, 7-5, 7-6 (1) in a match that lasted almost 2 1/2 hours; and American Steve Johnson reached his first career quarterfinal with a 6-3, 6-3 victory over American qualifier Tim Smyczek.