Serena Williams proved she is a genuine title contender at the Australian Open by knocking out fifth seed Nadia Petrova in the third round.
Williams won the title in 2003 and 2005
The former world number one recovered from a disastrous first set to triumph 1-6 7-5 6-3 in a gripping encounter.
Petrova looked poised to clinch victory when she roared through the first set and then served for the match at 5-4.
But Williams produced a typically gritty fightback and eventually prevailed after more than two hours.
The American said bravery was the key to her victory.
"I've always gone for my shots in any type of pressure situation, and I am going to keep it up," said Williams.
"It doesn't matter - I think the more pressure I get, the tougher I get.
She came up with some unbelievable returns
"I was down 3-5 and on the verge of being out of the tournament, and I obviously didn't want that to happen. It was time to either move or lose."
The twice former champion will face Jelena Jankovic in the last 16 after the in-form Serb saw off Victoria Azarenka, of Belarus, 6-3 6-4.
Short of match practice, Williams had been well below her best in her opening two matches and that form continued in the opening stages against the big-serving Petrova.
The Russian played solid tennis but she was grateful to 18 unforced errors from her opponent as she wrapped up the opening set in 19 minutes.
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In a see-saw second set, Williams raced into a 3-0 lead but then lost five games in a row to stand on the brink of defeat.
But the desperate situation brought out the best in the former world number one and at 4-5, she unleashed a string of punishing returns to get herself back into the match.
"She came up with some unbelievable returns," said Petrova later.
"She just went for the balls and she produced an unbelievable backhand winner up the line from far behind the court. That's what gave her confidence for the third set."
In an absorbing decider, Petrova clawed her way back from 0-2 down but Williams gritted her teeth again and clinched it when the fifth seed netted a service return.