Dushevina sprayed a forehand wide to give Williams two match points and then double-faulted to finish the match in exactly an hour in a swirling breeze at the Sydney 2000 Olympics venue.
Williams, playing her only warmup tournament ahead of her attempted title defense at the Australian Open, next plays France's Aravane Rezai, who had a 6-3, 6-0 win over Italian Flavia Pennetta.
She said the strong breeze was a relief after a hot opening win here, although experiencing both conditions was a good test before the season's first major starts Monday at Melbourne Park.
"It was really windy out there, but it's good to have a good result in the wind," she said. "I definitely don't think I played my best, but that's comforting to know that today wasn't my best."
Until this week, Williams hadn't played a tournament since she beat her older sister Venus in the final of the season-ending championship at Doha on Nov. 1. She said she had a lot of improving to do, and was aiming to be peaking at the end of the month.
"I always try to get there usually around the semifinals and finals of the Grand Slams," the 11-time major winner said. "I'm just doing the best that I can now to get there. Hopefully I have long way to go, which I think is always good."
No. 2 Dinara Safina was playing Olympic gold medalist Elena Dementieva later Wednesday in another quarterfinal _ a rematch from last year's Sydney final.
The winner will meet sixth-seeded Victoria Azarenka, who advanced 2-6, 6-2, 7-5 over Slovakia's Dominika Cibulkova.
On the men's side, Lleyton Hewitt started his bid for a fifth Sydney title with a 6-0, 6-2 win over Italian Andreas Seppi, reaching the quarterfinals with one 55-minute victory.
Former top-ranked Hewitt won six straight games, then overcame an early service break in the second set and won six straight games to finish when Seppi double-faulted at match point.
Fourth-seeded Hewitt, a former U.S. Open and Wimbledon champion, squared his career head-to-heads at 2-all with Seppi.
"I've had match points against him and ended up losing _ that scoreline today looks a lot better," Hewitt said.
Hewitt next plays 2006 Australian Open finalist Marcos Baghdatis, who ousted sixth-seeded Viktor Troicki of Serbia 7-5, 6-3.
Another Australian advanced to the quarterfinals when Peter Luczak had an upset 1-6, 6-4, 6-2 win over second-seeded Tomas Berdych of the Czech Republic.
Also advancing were Frenchmen Julien Benneteau and Richard Gasquet _ who beat eighth-seeded Benjamin Becker of Germany 6-2, 7-6 (4) _ and American Mardy Fish, a 6-1, 6-2 winner over Russia's Evgency Korolev.