Williams had a hitting session in Perth today and is expected to play for the United States against the Czech Republic after missing the opening matches against India.

"I just had the stomach flu. I was really sick and that's not very fun to have. But I'm good ... I recovered really fast," Williams said.

Meghann Shaughnessy substituted for Williams and won her match over Sania Mirza of India before Mardy Fish secured the 2-1 win.

"I was so glad when I heard that she won and Mardy won yesterday," said Williams, who won the 2002 Hopman Cup with James Blake. "I was really excited. I owe her a big thank you."

The Czech Republic lost 2-1 to Australia on Saturday.

Last year, Williams struggled in a warmup tournament in Hobart and was ranked 81st heading into the Australian Open. But she beat six seeded players en route to the Melbourne title.

She plans to take the week off before the Australian Open starts Jan. 14.

"Last year was cutting it close," Williams said. "I never really like to play a week before a Grand Slam. And especially as a defending champion, I really want to make sure I'm here trying to get ready.