updated 12:37 p.m. ET Jan. 23, 2008

MELBOURNE, Australia - It was a pretty tough 24 hours for the Williams sisters at the Australian Open.

Defending champion Serena Williams was outclassed by Jelena Jankovic in a quarterfinal on Tuesday, losing in straight sets. A few hours later, she and sister Venus — one of the most formidable doubles teams in Grand Slam history — lost their quarterfinal match to China’s Yan Zi and Zheng Ji in three sets.

A night’s sleep didn’t help Venus Williams on Wednesday, when she lost her singles quarterfinal 7-6 (3), 6-4 to Ana Ivanovic of Serbia.

A combined and unexpected 0-for-3, sending the Williams sisters packing for home.

“What’s important to me is what goes on in my head,” Venus Williams said after her loss to 20-year-old Ivanovic. “I’ve been a champion. I have full expectations and aspirations to continue to play high-quality tennis and to continue to be a champion.”

Serena has eight Grand Slam singles titles, including last year at Melbourne Park. Venus has never won here, but has six majors elsewhere, including last year at Wimbledon.

Together, they have combined for six Grand Slam doubles crowns — Wimbledon and the Australian Open twice and the French Open and U.S. Open once each — and the gold medal at the 2000 Olympics.

“Serena and I, we don’t have anything to prove,” Venus said. “We get out there and we play our best. I think the way we’re playing still maintains what other women are doing in tennis. So I think we still set a very high standard.

“Players are still playing very well. Everyone’s improving. I don’t get too caught up in what the next person thinks.”

It’s difficult to forget the Williams sisters in their prime, in particular the celebrated “Serena Slam,” when the younger of the two siblings held all four Grand Slams at once — the 2002 French Open, Wimbledon and U.S. Open and the ’03 Australian.

Serena beat Venus in each of those championship matches. And Venus won four Grand Slams from 2000-01, including beating her sister in the 2001 U.S. Open final.

At the time, talk centered on how women’s tennis had become predictable because the Williams sisters won so frequently.

Five years later, Venus jokingly thinks she and her sister may have been the architects of their own demise.

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“Yeah, I guess it’s my own fault, huh?” Venus said, smiling. “Maybe I should serve a little softer, not run as fast. But I think everyone’s playing better, everyone’s hitting a good ball, trying to hit harder, run faster and serve bigger.”

She wouldn’t speak for her sister, but Venus believes she still has enough to win another Grand Slam. The Australian Open has so far eluded her, the nearest miss coming when she lost the 2003 final to Serena.

“I’m still improving. That’s my goal, to be better at every tournament,” Venus said. “If I don’t have that goal one day, then that’s a problem.

“I would love to win here. I still think that I can. Unfortunately, it won’t be this year.”

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