Elena Dementieva wore down Slovakia's Daniela Hantuchova 7-5, 5-7, 6-4 in a rollercoaster match on Saturday to book her place in the fourth round of the Australian Open.
Dementieva, runner-up at last year's French and U.S. Opens, won a see-sawing match that lasted almost three hours and featured 13 service breaks.
Dementieva dropped serve six times and made 78 unforced errors but the 23-year-old said she was encouraged by the fact she was still able to win.
"It was a tough match but I feel like I didn't play my good game," sixth seed Dementieva said.
"I think it's pretty much impossible to play your best tennis for two weeks so it can't be that bad to go through this.
"Even though I played very bad today and I was very defensive, I still did it."
Despite her success last year, Dementieva has been dogged by serving problems.
She had to fight back from a break down to win the opening set against Hantuchova and lost the second after she served for the match at 6-5.
The Russian broke Hantuchova twice at the start of the deciding set but allowed the Slovakian to pull one back before finally holding her nerve to seal victory.
"Even though I didn't play my best today I know that I can do it," she said.
"I know how well I can play. All I need is to have a good rest now and play as good as I can for the next round."
Dementieva plays Patty Schnyder in the fourth round after the Swiss 12th seed beat American Abigail Spears 7-6, 6-3.
Dementieva beat the Swiss in Sydney last week but said she remains wary of her.
"We know each other very well, she's a left-handed player," she said.
"She's a tough player for me. I'm sure I'll have to play much better than today to beat her."