"I've been doing the hard yards on and off the practice court," Hewitt said. "I feel as fit as I've ever been and I feel as strong as I've ever been and I'm hitting the ball well at the moment."
The 28-year-old Hewitt's ranking slumped to 108 in February following hip surgery but the Australian has since improved to No. 22, with a quarterfinal appearance at Wimbledon and an ATP title win at Houston.
"If the body holds up then there's no reason why I can't give all these guys a run," Hewitt added.
Hewitt, winner of the 2001 U.S. Open and 2002 Wimbledon title, said he would need luck to fall his way if he is to win the Australian Open beginning Jan. 18. The closest he came was in 2005 when he lost to Marat Safin in the final at Melbourne Park.
"A lot depends on the draw," Hewitt said. "At least I'll be seeded and hopefully get a smooth passage through. If I can get through the first week and put myself in a (good) position in the second week there's no reason why I can't do some serious damage."
Hewitt will partner Sam Stosur at the Hopman Cup mixed teams event, with top-seeded Australia taking on Romania's Sorana Cirstea and Victor Hanescu in the first group match on Saturday.
Host country Australia has only won the Hopman Cup once, in 1999.
The United States, represented by U.S. Open quarterfinalist Melanie Oudin and John Isner, will play its first match Sunday against Maria Jose Martinez Sanchez and Tommy Robredo of Spain. The U.S. has won the event five times and been runner-up on four occasions.
Andy Murray and 15-year-old Laura Robson are representing Britain. Australia and Britain could only meet in the final as the countries are playing in opposite groups. The winner of each group plays in the final on Jan. 9.
"Andy Murray is ... such a quality player but he's playing with a young girl, so how they actually fare in this competition is going to be up in the air," Hewitt said.
Russia is the top-seeded team in Group B, with Igor Andreev to partner Elena Dementieva.
Each contest between countries consists of a men's singles, women's singles and mixed doubles match.