A lone guitarist welcomes the crowds into Melbourne Park as day five of the Australian Open gets under way amid glorious sunshine

Nadia Petrova, the 10th seed, becomes the first woman to reach the last 16 when her opponent Galina Voskoboeva retires hurt

Petrova later celebrates her victory by heading down to Brighton Beach for a quick paddle

Third seed Dinara Safina plays her best tennis of the tournament so far to dispatch a disappointing Kaia Kanepi 6-2 6-2

Fernando Verdasco relaxes with some penguins on the rest day ahead of his third-round match match against Radek Stepanek

British number one Anne Keothavong and her partner Mervana Jugic-Salkic are knocked out by Maria Kirilenko and Flavia Pennetta

Juan Martin del Potro fails to hide his frustration after losing the first set of his match against Luxembourg's Gilles Muller on a tie-break

Del Potro fights back against Muller, hitting some fine groundstrokes and booming serves en route to a 6-7 (5-7) 7-5 6-3 7-5 victory

Next up for Del Potro is 19th seed Marin Cilic, the Croatian cheered to the rafters as he beats 11th seed David Ferrer in straight sets

Defending champions Novak Djokovic looks set for a comfortable passage to round four after easing to the first set against Amer Delic

But lucky loser Delic, a Bosnian-born America, rallies to stun the world number three by taking the second set and levelling at 1-1

The trainer is called to help Delic patch up his blistered feet and Djokovic is able to wrap up the third set with one break

Delic sees two set points go begging in the fourth before Djokovic comes through on a tie-break to win 6-2 4-6 6-3 7-6 (7-4)

Vera Zvonareva looks in top form as she beats Italy's Sara Errani in straight sets to set up a meeting with fellow Russian Petrova

Marion Bartoli, the 16th seed, comes from a set down to beat unseeded Czech Lucie Safarova 3-6 6-2 6-1

No problems for seventh seed Andy Roddick as he powers his way to a 6-3 6-4 6-2 win over French veteran Fabrice Santoro

Alize Cornet, the 15th seed, comes from a set down to beat 19th seed Daniela Hantuchova 4-6 6-4 6-2

Top seed Jelena Jankovic is made to work hard for a 6-4 6-4 win over Ai Sugiyama in an hour and 41 minutes

Tough going for Ana Ivanovic, the sixth seed, as she loses to Russian teenager Alisa Kleybanova 7-5 6-7 (5/7) 6-2

But Kleybanova celebrates the best win of her career, knocking out last year's beaten finalist in Melbourne

Marat Safin reflects on what could be his last Australian Open after losing to Roger Federer 6-3 6-2 7-6 (7/5)

Federer remains focussed to beat Safin for the 10th time in 12 matches and progress to round four