Andy Murray booked a quarter-final place at the SAP Open in San Jose with a 6-4 6-2 win over Yeu-Tzuoo Wang.
Murray will face Swede Robin Soderling in the quarter-finals
The 18-year-old fell 3-0 behind in the first set but after pulling level, he survived a marathon eighth game on his own serve before taking the first set.
"I think the first set was the toughest I've played on the tour," he said.
Murray roared through the second set to set up a quarter-final meeting with Sweden's Robin Soderling, who beat Australian Mark Philippoussis.
It will be Murray's first ATP quarter-final of the season, and only the third of his career.
Victory over Soderling on Friday would set up a possible semi-final with top seed Andy Roddick, if the American beats Germany's Bjorn Phau.
Roddick survived a torrid second set before beating Dane Kenneth Carlsen to seal a quarter-final against Phau.
The 23-year-old won the opener 6-3 but surrendered the second 6-1 before recovering to win the decider 6-3.
Third seed Lleyton Hewitt had little trouble beating American Sam Warburg 6-4 6-3 but he said the ankle injury he suffered in his second-round defeat at the Australian Open was still bothering him.
"I still feel it out there," Hewitt said.
"It's just when I jam my foot off during matches. It's something you can't test before a match. So I'm just trying to build it up."
Hewitt meets fellow Australian Wayne Arthurs in the quarter-finals after the veteran upset seventh seed Dmitry Tursonov 6-3 6-7 6-3.