British number three Andy Murray will face Taiwan's Yeu-Tzuoo Wang in the second round of the SAP Open in San Jose on Thursday.
Murray beat Mardy Fish in straight sets in the opening round
Wang caused a major upset with a 6-3 7-5 win over American James Blake on Wednesday for his first victory against a top-20 player.
"I felt a lot of confidence," said the 21-year-old. "I took my chances and stayed within my rhythm."
Also on Tuesday, top seed Andy Roddick beat Guillermo Garcia-Lopez 6-3 6-4.
Roddick is still recovering after vomiting on court in a five-set Davis Cup match against Romania's Andrei Pavel last week.
"Last Friday was the worst I ever felt after a tennis match," said Roddick.
"I was completely drained but had a day off yesterday and will have a day off tomorrow, so it shouldn't be a challenge to continue."
On Wednesday, third seed Lleyton Hewitt will make his first appearance since the Australian Open when he takes on American Paul Goldstein, and John McEnroe returns to the ATP Tour to play doubles with Jonas Bjorkman.