Serena Williams started her 2010 season in the same devastating fashion in which she ended 2009, thrashing Spain's Marie Jose Martinez Sanchez 6-1 6-2 in the second round of the Sydney International yesterday.

Playing her first match since beating older sister Venus in the final of last year's Tour Championship, Williams showed why she remains the woman to beat at this month's Australian Open with a powerful display.

The world number one was not at her absolute best after a two-month break and struggled with the scorching temperatures at the Olympic tennis centre, but could not have been happier with her form leading into the first grand slam of the year.

"I felt all right. Obviously I don't feel my best, but that's what the game is all about, taking it one match at a time and just doing the best that you can," she told reporters.

"My goal is to do well but I can't put too much pressure on myself. If I play the best I can play, I've always said I'm very difficult to beat."

Russia's Dinara Safina, who lost last year's Australian Open final to Williams, also opened her new season with a win but had to work much harder before toppling Poland's Agnieszka Radwanska 7-5 6-4 to advance to the quarter-finals.

Safina spent the off-season recovering from a back complaint and the early signs were not good when she lost the first five games of the match as the mercury hovered above 35 degrees Celsius.

But just when the world number two looked to be in trouble, she rebounded and seized control of the contest.

Russia's defending champion Elena Dementieva beat Slovakia's Daniela Hantuchova 6-2 4-6 6-2 while Victoria Azarenka of Belarus defeated Kimiko Date Krumm of Japan 6-1 5-7 7-5, leaving four of the original eight seeds in the women's draw.

The only high-profile casualty was Russia's French Open champion Svetlana Kuznetsova, who was beaten 7-5 6-2 by Dominika Cibulkova of Slovakia.