Daria Gavrilova has been dudded by a 'horrendous' call in the second set of her second-round loss to Elise Mertens at the Australian Open late on Wednesday night.

The Australian No.2 suffered a heartbreaking 7-5 6-3 loss after holding a 5-0 first-set lead, but it was a controversial blow-up with the umpire that marred the second set.

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Gavrilova was rocked when, trailing 4-2, she tried to challenge an incorrect ruiling but umpire Aurelie Tourte said she was too late and had looked to her box first.

The pair spent nearly a full minute arguing before the Tourte forced the player back for the next point by calling an end to the point.

"I'm challenging the ball, I said it straight away, I'm challenging the ball," Gavrilova fumed to the umpire.

"There is no friggin' way you can't call it a challenge."

Gavrilova wasn't happy with the umpire. Pic: Getty More

Commentators described it as a "horrendous call" but Gavrilova, who argued on Rod Laver Arena that she had looked at the big screen before challenging rather than her box.

But she conceded after the match that her coach Jarryd Maher had signalled something at the time.

"She (Tourte) said my coach told me to but he did go like that (pointed upwards) but that could have meant anything," she said.

Mertens went on to secure the double break and although Gavrilova broke back, she was visibly upset and continued the argument with the umpire following the loss:

The 23-year-old served 10 double faults for the match, which became the latest to start in Australian Open history when it began at 11.59pm, while her unforced errors went through the roof with a total of 40.

Gavrilova had four set points at 5-0 but was unable to convert and then missed another four opportunities as the Hobart champion edged her way back.

The world No.23 wasn't aware of how many set points she had blown until the post-match press conference.

"That sucks," she said.

"I can't believe it got away from me but it just happened and it happened quickly.

"I've seen players lose before from 5-0 up and thought, surely they could have just hit a winner but clearly I couldn't so it's a new experience."

Gavrilova has enjoyed a stellar Open run, making the fourth round in the past two years, while this was Mertens' Melbourne Park debut.

The Belgian will face Alize Cornet of France in round three.

with AAP