Serena Williams joined Alicia Molik as a quarter-final casualty on Wednesday night as the top two drawcards crashed out of the Hobart International.

Molik, targeting her first WTA semi-final berth in nearly two years, was gunned down 6-4 6-1 by close friend and doubles partner Sania Mirza before former world No.1 Williams - playing her comeback tournament after knee surgery - bowed out 3-6 7-5 6-3 after simply running out of puff against fired-up Austrian Sybille Bammer.

"I've never seen her play like this before in my life. I guess she was just up to play me," Williams said of the world No.56.

"I don't think I played that well, I made a lot of unforced errors, but I just think I'm a little rusty so I've just got to try and shake it off for Melbourne (the Australian Open).

"I just got a little bit sore (in the third set), but I wasn't really tired. My body was just feeling sore."

While her run in Hobart came to a screeching halt, Molik believes she will still carry momentum into the Australian Open.

The Australian was scathing of her own serve after her match and promised to hit the training court hard over the coming days before next week's grand slam in Melbourne.

But after a pair of wins in Hobart earlier this week, the former world No.8 - who has worked her way back to 165 in the rankings after an injury and illness-plagued 18 months - believes she will carry plenty of confidence into the Open.

"Absolutely, I've had three matches here in singles, I would have loved to have won today but it didn't go my way. It just means I'll get out there and work harder tomorrow," said Molik, who tipped Mirza to win her second WTA title at Hobart on Friday.

"There's a couple of things I'd really like to work on over the next few days but I think often you learn more from your losses than your wins. Certainly I think I do."

In particular, the 25-year-old will focus on her serve, which she branded as "unacceptable" today.

Molik also bowed out of the doubles today after she and Mirza lost 7-6 (7-5) 7-6 (7-1) to Maria Elena Camerin and Gisela Dulko.

The match was played just 90 minutes after their singles clash.

Having already toppled fourth seed Maria Kirilenko in the first round, Mirza meets top seed Anna Chakvetadze in Thursday's semi-finals. The Russian defeated seventh-seed Jie Zheng 4-6 6-1 6-1.

Compatriot Vasilisa Bardina plays Bammer in the other semi after she triumphed 3-6 6-2 7-5 in a gruelling three-hour match against Catalina Castano.

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