Mertens downs distressed Cornet to reach last 16

Melbourne - Elise Mertens reached the fourth round of the Australian Open in straights sets on Friday after a dramatic match in which her opponent Alize Cornet needed a doctor.

Belgian world number 37 Mertens won 7-5, 6-4 in just over two hours of energy-sapping tennis on Hisense Arena as temperatures touched 40 Celsius. 

"It's hot," said the in-form Mertens, who is coming off a successful title defence at Hobart last week and is now into the last 16 of a Grand Slam for the first time. "The toughest I have had."

It was her French opponent however, who wilted in the heat in distressing scenes with the score at 2-1 in the second set. 

Cornet was struggling to breathe as her blood pressure and pulse were monitored by the doctor on court during a medical timeout. 

Ice towels were applied and ice packs rubbed over her face, arms and legs in a frantic attempt to cool the player ranked 42. 

Cornet sat with her eyes closed, gasping for breath before resuming, clearly still wobbly. 

She somehow recovered enough to fight back from 5-2 down to 5-4, saving three match points in the final game which went to five deuces before her gutsy resistance was ended. 

"Credit to her for keeping going," said Mertens, who threw her racquet down in disgust after spurning her third match point, only to scream with joy a few moments later when she finally sealed the deal. 

Mertens now faces Petra Martic for a place in the quarter-finals after the Pole edged Thailand's Luksika Kumkhum 6-3, 3-6, 7-5.

Results from the Australian Open on Friday:

Men's singles

3rd round

Kyle Edmund (GBR) bt Nikoloz Basilashvili (GEO) 7-6 (7/0), 3-6, 4-6, 6-0, 7-5

Women's singles

3rd round

Petra Martic (CRO) bt Luksika Kumkhum (THA) 6-3, 3-6, 7-5

Denisa Allertova (CZE) bt Magda Linette (POL) 6-1, 6-4

Elise Mertens (BEL) bt Alize Cornet (FRA) 7-5, 6-4

Elina Svitolina (UKR x4) bt Marta Kostyuk (UKR) 6-2, 6-2