A defiant Serena Williams [Images] surged into the semi-finals of the Australian Open [Images] on Tuesday before lashing out at critics who have suggested the Williams sisters are past their best.

The former world number one thrashed second seed Amelie Mauresmo [Images] 6-2, 6-2 to reach the last four and insisted she had nothing to prove, even though it is now 18 months since she last won a grand slam title.

Her sister Venus, without a grand slam title since Wimbledon [Images] in 2001, was beaten in the fourth round at Melbourne [Images] Park but an angry Serena said that claims the Williams sisters are in decline were unfair.

"I don't appreciate that language, to be honest with you," she said.

"I'm tired of not saying anything, but that's not fair. We've been practising really hard. We've had some serious injuries.

"I mean, I've had surgery. And after surgery, I got to the finals of Wimbledon. I don't know too many people that have done that."

SERIOUS INJURIES

In the last 16 months, both Williams sisters have been off the tour for periods with serious injuries, while they also suffered the loss of their eldest sister, Yetunde Price, who was killed in a shooting incident in Los Angeles in September 2003.

"Venus had a severe strain in her stomach," Serena said.

"I actually had the same injury, but I didn't tear it the way she did. If I'd have torn it, I wouldn't have been here. She played a player yesterday (Alicia Molik [Images]) that just played out of her mind.

"And to top it off, we have a very, very, very, very, very close family. To be in some situations that we've been placed in in the past little over a year, it's not easy to come out and just perform at your best when you realise there are so many things that are so important.

"So, no, we're not declining. We're here. I don't have to win this tournament to prove anything. I know that I'm out here and I know that I'm one of the best players out here."

In searing heat and against a Mauresmo who said she was only 50 percent fit because of an adductor strain, Williams turned in an impressive performance, cutting down her errors to clinch a comfortable victory.

In the semi-finals, Serena will meet fourth seed Maria Sharapova [Images] in a repeat of last year's Wimbledon final, which the Russian won.

"I think (Sharapova) is a really mentally tough character out there," she said.

"I feel like I don't have anything to lose. I think I was way too nervous at Wimbledon. I couldn't sleep, I couldn't breathe. Sometimes you want it too bad that you just freak yourself out."

"Now I feel fine. I'm really proud of myself, doing pretty well with my preparation here."

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