MELBOURNE, Jan. 18 -- On day four of the Australian Open, one could make the argument that the biggest winners on the day were not the players, but probably the vendors selling ice cream and water bottles.

Scorching weather conditions on Thursday saw temperatures rise above 40 degrees Celsius and as a result many big names struggled.

Up first on centre court was a hit out between former world number one, Maria Sharapova, and 14th seed Anastasija Sevastova.

Although many expected a tight contest, Sharapova cruised to victory and won in straight sets.

"It was warm! And it got warmer as the match went on," an exhausted Sharapova told Xinhua.

"Sometimes when you toss the ball up serve, the sun was a problem, but I liked that we were out there a bit earlier."

For those on a bit later in the day, the stifling heat was brutal.

During his second round match with Novak Djokovic, Frenchman Gael Monfils told the umpire he would "collapse," if he kept enforcing the 25-second rule before each service.

Although Djokovic won the tussle in four sets, the Serbian looked far from his best, missing a number of backhand shots and committing several uncharacteristic double faults.

The biggest shock of day came when 2017 Australian Open champion Stan Wawrinka crashed out in straight sets to world number 97, American Tennys Sandgren.

Wawrinka was suspected to have a knee injury going into the tournament and clutched it throughout the contest.

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