Top seed and four-time winner Andre Agassi and fellow American Vincent Spadea -- the third seed -- withdrew Tuesday with injuries, leaving the second-seeded Philippoussis.

Agassi experienced altitude sickness and dehydration during his final Davis Cup match in Zimbabwe, had severe cramps and back spasms during his 24-hour trip from Harare to the Bay area, where he felt more back pain during Tuesday afternoon's practice session. Agassi will have an MRI today.

American Scott Humphpries of the United States took Agassi's spot in the draw and will play Mark Woodforde of Australia tonight.

Spadea withdrew Tuesday with a shoulder injury and was replaced by lucky loser Xavier Malisse of Belgium, who beat Australian Richard Fromberg on Tuesday and takes on Paul Goldstein of the United States today.

Like Agassi, Philippoussis is fresh off Davis Cup first round play in which his country came from 1-2 back to win. He lost his first singles match to Roger Federer of Switzerland on Friday but came back to defeat George Bastl, 6-7 (4-7), 6-4, 3-6, 6-3, 6-4, to lift Australia to victory. Philippoussis lost to Agassi in the fourth round of the Australian Open.

In second-round action, fifth seed and 1992 runner-up Jim Courier of the United States faces Hernan Gumy of Argentina and No. 7 Wayne Ferreira of South Africa encounters Finnish qualifier Ville Liukko today.

The 29-year-old Courier posted a 6-3, 6-4 victory over countryman Eric Taino on Tuesday. He had lost his only previous match of the season to Nicolas Escude in the first round of the Australian Open. His form was so poor that he was left off the Davis Cup team that beat Zimbabwe last weekend.

"I caught the flu in January but I have overcome that," said Courier, a former No. 1 who is without a tournament victory in almost two years. "I know how to win matches so it's just match experience that I need to get back into things. There is no one here, I don't think, that I can't compete with."

In two second-round matches involving non-seeded players, Sargis Sargsian of Armenia goes against John Van Lottum of the Netherlands and Nicolas Massu of Chile battles Tomas Zib of the Czech Republic.

First prize is $49,500.