Australian Open 2014: day four – in pictures

Maria Sharapova overcame remarkable resistance from the world No44, Karin Knapp, but hung on to eventually win 6-3, 4-6, 10-8 in an epic lasting three hours and 28 minutes Photograph: Cameron Spencer/Getty Images

With the brutal and oppressive heat continuing in Melbourne, when the temperature hit 42C (108F) the organisers implementing the Extreme Heat Policy. This meant the roof of the Rod Laver and Hisense arenas were closed and play on the outer courts was stopped at the end of sets that were in progress Photograph: Quinn Rooney/Getty Images

Former world No1 Caroline Wozniacki went the distance before finding a way past Christina McHale 6-0, 1-6, 6-2 Photograph: Joe Castro/EPA

World No1 Rafael Nadal was up against the lowest ranked player in the tournament, world No570 Thanasi Kokkinakis. The 17-year-old didn't seem fazed and put in a hugely impressive performance, but the top seed fought off his challenge to win 6-2, 6-4, 6-2 Photograph: Mark Kolbe/Getty Images

Nadal gets rid of some of the sweat he amassed during his match Photograph: Franck Robichon/EPA

Defending champion Victoria Azarenka cruised into the third round courtesy of a straight sets 6-1, 6-4 win over Barbora Zahlavova Strycova Photograph: Jason O'Brien/Action Images

It's a packed house in the Rod Laver Arena to see Andy Murray take on Vincent Millot Photograph: Cameron Spencer/Getty Images

Andy Murray is in total charge of the first set and takes it 6-2 Photograph: Cameron Spencer/Getty Images

Murray is equally as focussed during the second set which he also takes 6-2 Photograph: Jason O'Brien/Action Images

Millot comes back in the third and goes 5-2 up and gets to set point, however Murray seems to take this as a personal affront and then rattles off an extraordinary run of 23 consecutive points to win the match 6-2, 6-2, 7-5 Photograph: Cameron Spencer/Getty Images

The unseeded Elina Svitolina beat wildcard Olivia Rogowska in straight sets, 6-4, 7-5 Photograph: Michael Dodge/Getty Images

Jo-Wilfried Tsonga's fans were pleased with his 7-6 (8-6), 6-4, 6-4 victory over Thomaz Bellucci Photograph: Paul Crock/AFP/Getty Images

Roger Federer was taken to a tie-break in the final set of his 6-2, 6-1, 7-6 (7-4) straight sets victory over Blaz Kavcic Photograph: Jason O'Brien/Action Images

Alizé Cornet had reason to celebrate after being pushed to three tight sets before seeing off the challenge of Camila Giorgi 6-3, 4-6, 6-4 Photograph: Quinn Rooney/Getty Images

Sloane Stephens overcame a first set hiccup to knock out the unseeded Ajla Tomljanovic 3-6, 6-2, 7-5 Photograph: William West/AFP/Getty Images

Benoit Paire was frustrated on a number of occasions by the unseeded Nick Kyrgios who went two sets ahead in their match before the number 27 seed came back and finally made it through to the third round 6-7 (5-7), 6-7 (5-7), 6-4, 6-2, 6-2 Photograph: Eugene Hoshiko/AP

The upset of the day came on Court Two where fifth seed Juan Martin Del Potro eventually succumbed to Roberto Bautista Agut after a mammoth five set battle. The unseeded player triumphed 4-6, 6-3, 5-7, 6-4, 7-5 Photograph: Jason Reed/Reuters

Donald Young ground out a well deserved victory over 24th seed Andreas Seppi in an epic five setter, which the unseeded American won 6-4, 2-6, 6-3, 4-6, 7-5 Photograph: Andrew Brownbill/AP

Andy Murray's brother Jamie was in action in the doubles where Murray, left, and John Peers overcame the spirited resistance of Matt Reid and Luke Saville to win 7-6 (7-4), 7-6 (8-6). Murray needed urgent medical attention in the locker room after the match after collapsing with heat-stroke Photograph: Scott Barbour/Getty Images

There were baking conditions out on Court Six where Kei Nishikori's fans did whatever they could to keep themselves cool while watching the No16 seed overcome Dusan Lajovic 6-1, 6-1, 7-6 (7-3) Photograph: Saeed Khan/AFP/Getty Images

However, if the darkening sky and lightning are anything to go by, there might be some respite on the way for the players and fans. Click here to see more pictures of how fans and players dealt with the Melbourne heatwave Photograph: Robert Prezioso/Getty Images