Serena Williams can still see room for improvement in her game despite racking up her 17th successive win at the Australian Open today.
The American has not lost in Melbourne since being stunned by Jelena Jankovic in the 2008 quarter-finals.
Yet she comes into the tournament as the 12th seed and with questions surrounding her fitness - she missed last year's event with a foot injury and the subsequent discovery of a blood clot on the lung gave her another sizeable hurdle to overcome.
But on the evidence of the first week she remains the woman to beat.
Williams was far too good for Greta Arn in their third-round clash, easing to a 6-1 6-1 win in under an hour.
The 13-time grand slam champion has dropped just 11 games in reaching the fourth round but believes there is more to come.
"I can hit a little deeper and better, be more consistent," she said.
"Hopefully that will come as I keep playing."
Given her lack of match practice, Williams could have been forgiven for feeling under-cooked heading into week two but she is quite happy with how things are progressing.
"I'm pretty experienced so I kind of know what the feeling of having tough matches is, and having simple matches is, so it's okay," she added.
Another player on the comeback trail is Ana Ivanovic and she moved a step closer to her first grand slam quarter-final in three and a half years following her defeat of Vania King.
Ivanovic has not made the last eight at a major since winning the 2008 French Open, after which she became the world number one.
It appeared she was set to be a contender for the foreseeable future only to suffer a slump which led to fears she was approaching also-ran status on the WTA Tour.
However, her results have improved since linking up with new coach Nigel Sears and reaching the fourth round at the US Open last year was an indication she was regaining her best form.
She certainly looked good in beating American King 6-3 6-4, despite battling a bug which laid her low yesterday.
Standing between her and a place in the quarter-finals is second seed Petra Kvitova, the Wimbledon champion.
"I always want to take it one match at a time but the next match could get me there (the quarter-finals)," said Ivanovic.
"But it's going to be a very tough one.
"Petra is definitely playing some great tennis, she's one of the hottest players at the moment. It's going to be a great challenge for me.
"But I'm really happy to go out there and throw my best at her. The better player will win."
Ivanovic will have her work cut out if she is to reach the quarters as Kvitova will be fresh after her match with Maria Kirilenko lasted just seven games before the Russian pulled out through injury.
After breaking three times, and displaying her best tennis in the tournament to date, Kvitova romped to a 5-0 lead, at which point Kirilenko had to leave Rod Laver Arena for a medical timeout.
The Russian returned with heavy strapping on her upper left leg and despite her best efforts to make it a contest, Kvitova clinched the opening set and the first game of the second before Kirilenko called it a day at 6-0 1-0 down.
"What I played in the first five games was great," said the Czech.
"It was really different to what I did in the last match and I am really happy. Hopefully it will continue like this."
Maria Sharapova also advanced with a 6-1 6-2 defeat of German Angelique Kerber.
Kerber, a semi-finalist at the US Open last year, was expected to provide the fourth seed with her first serious test of the tournament but it never materialised as Sharapova eased through to a meeting with Sabine Lisicki, a 2-6 6-4 6-2 victor over Svetlana Kuznetsova.
"It was a really good first set and she stepped it up in the second," Sharapova said.
"She was in the semis at the US Open and she has been on this stage before so I know she could produce some good tennis.
"The second set was certainly closer than the scoreline suggests."
Seventh seed Vera Zvonareva was beaten 7-6 (9/7) 6-1 by Ekaterina Makarova, who will next play Williams, while Sara Errani will face Jie Zheng.
Errani beat Sorana Cirstea 6-7 (6/8) 6-0 6-2 while Jie overcame ninth seed Marion Bartoli 6-3 6-3.