Ash Barty revealed a glimmer of frustration at the Madrid Open after a third round scare from world No.80 Tamara Zidansek.
The Australian superstar claimed a rollercoaster three set win over the 23-year-old Slovenian player 6-4, 1-6, 6-3.
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It looked for all money as though the wheels had fallen off for Barty in the second set, with Zidansek breaking her serve twice on the way to a surprisingly one-sided frame.
Barty was able get it together by the third set, racing to a 3-0 lead, but her frustration was palpable after her opponent challenged a let service call, changing it from in to out.
An irritated Barty took up the issue with the chair umpire a short time later.
“You know the system is as much bulls*** as I do, don’t you," Barty was heard saying.
Fortunately for the world No.1, once she got rolling there was no stopping her in the third set, steamrolling Zidansek to set up a intriguing clash with reigning French Open champion Iga Swiatek.
It will be the first career meeting for the pair.
World No.14 Swiatak progressed to their round of 16 clash in Madrid with a 6-3 6-3 win over Germany's Laura Siegemund.
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Barty revealed she'd watched just a fraction of the 2020 French Open, having turned on the TV in Australia and accidentally caught a snippet of early rounds action, long before Swiatek astonished Paris.
"There was no frustration, absolutely not. I know I made the decision to not go and play for the right reasons," she recalled.
"I have absolutely no regrets about that.
"It was tough to come to terms with knowing I wasn't able to go and try to defend my title, but it's all good. I get another opportunity in a few weeks' time."
Barty reckoned she'd had a "really tough" tune-up for Swiatek from the world No.80 Zidansek.
The Australian struggled with her serving, made "too many loose ones" - 31 unforced errors - and lost a touch of focus in the second set before, typically, coming up clutch in the decider. Barty's now won 10 of her 11 three-setters this year.
She can't wait for the Madrid roof to be opened after having now played two 'indoor' matches - and the forecast bodes well for an open air duel on Monday.
"I'm desperate for a bit of sunshine, get out in some more heat. Once the roof is open, the sun comes out, it's a different ball game again," said Barty.
Swiatek, the world No.17 who's rising fast and won her second WTA title in the Adelaide International in February, said she felt she was the underdog.
"I really respect her ... It seems too easy for her," said Swiatek, praising what she felt was Barty's healthy perspective on winning and losing.
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