Melbourne, Jan 18 (Agencies): Tennis star Venus Williams sent out a warning to her competitors as she outshone some of her biggest rivals on day one of the Australian Open.

Williams overcame a sluggish start to overpower Italy’s Sara Errani 6-3, 6-2, as top seed Caroline Wozniacki, former winners Maria Sharapova and Justine Henin, and French Open champion Francesca Schiavone all struggled to impress.

Wozniacki took 1hr 40min to see off Gisela Dulko 6-3, 6-4, Sharapova struggled with her serve before beating Tamarine Tanasugarn 6-1, 6-3, and Henin had to pull out all stops to beat Indian qualifier Sania Mirza 5-7, 6-3, 6-1.

Meanwhile French Open champion Schiavone lost the first set to Arantxa Parra Santonja before eventually winning 6-7 (4/7), 6-2, 6-4.

Williams, the United States’ best hope in the absence of her injured sister Serena, the current champion, risks being underdone after not playing a WTA tournament since the US Open.
“It’s only just a matter of believing that I can come out and play well even though I haven’t played as much as my opponents,” said Williams, who warmed up with an exhibition tournament in Hong Kong.

“I worked as hard as I could in the off-season -- I worked hard to be here.”

Williams has been something of an under-achiever at the Australian Open, reaching the final once, in 2003, but often falling early to unheralded opponents.

She lost in the 2010 quarter-finals to China’s Li Na and went down in the second round in 2009 to Carla Suarez Navarro of Spain.

Earlier Wozniacki, under pressure to claim a maiden Slam title to convince critics she is a deserving women’s number one, laboured to subdue 52nd-ranked Dulko, who made 38 unforced errors during the match.
And former champion Sharapova admitted she had room for improvement after her win over 33-year-old Tamarine.

Sharapova has already bettered last year’s performance, when she was shocked in the first round by fellow Russian Maria Kirilenko.

“I was definitely a little bit nervous in the beginning,” Sharapova said.

“Last year I played the first match on centre court and I lost, so I was like, I don’t want this to happen again this year.”

Henin, who won the Australian Open in 2004 and finished runner-up in 2006 and 2010, needed all her legendary fighting qualities to subdue an inspired Mirza in 2hr 12mins in a torrid first round clash.

“I think I needed this kind of match exactly to really be into the tournament like I want to be and be at my best level,” Henin said.

“I have the experience, but I need matches, I need rhythm, and I need fight, like tonight.”

China’s Li Na, who reached last year’s semi-finals and is fresh from victory at the Sydney International, went through against Sofia Arvidsson of Sweden 6-1, 7-5, while eighth seeded Belarusian Victoria Azarenka thrashed German Kathrin Woerle 6-0, 6-2.

Other seeded players to progress were France’s 15th ranked Marion Bartoli, who trounced Italian Tathiana Garbin 6-0, 6-0, Estonian Kaia Kinepi (20), who beat Magdalena Rybarikova 2-6, 6-4, 6-3 and Slovakia’s Dominika Cibulkova (29), a 6-2, 6-7 (4/7) 6-4 winner over German Angelique Kerber.

Belgian’s 21st ranked Yanina Wickmayer ended the hopes of Australian Jarmila Groth 6-3, 2-6, 6-4.

There were two minor upsets, 17th seeded Frenchwoman Aravane Rezai going down to Czech Barbora Zahlavova Strycova 6-0, 3-6, 7-5 and Russia’s Regina Kulikova downing 28th ranked Slovakian Daniela Hantuchova 7-6 (7/3), 3-6, 9-7.