Petra Kvitova has beaten Ash Barty 1-6 7-5 7-6(3) in an epic Sydney International final at Ken Rosewall Arena.
Barty opened the final in ominous form, taking just 25 minutes to win the first set, before Kvitova fought back late in the second.
Kvitova needed three chances to seal the win after being broken twice while serving for the match.
Up 6-5 in the third set, Kvitova's service game went to pieces as she served her eighth and ninth double faults of the match and Barty forced a tie-break.
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Appearing to be suffering from cramp in the hot conditions, Kvitova was finally able to hold her nerve in the tie-break, needing just one of her three championship points to seal it.
Earlier in the match, Barty broke Kvitova three times in a dominant first set, including the former two-time Wimbledon champion's first two service games of the final.
As had been the case for most of the week, Barty held serve with relative ease, while a powerful forehand applied pressure and her sliced backhand dictated tempo.
What a start from Australia's @ashbar96 🔥
— #SydneyTennis (@SydneyTennis) January 12, 2019
📹: @Channel9 @9Gem #SydneyTennis pic.twitter.com/FbXMsuhdHb
Kvitova finally started making shots in the second set, but it wasn't until Barty's sixth service game that the Czech player finally earned her first break point and sent the final into a deciding third set.
The pair traded breaks early in the third frame, before Kvitova - who won five titles in 2018 - broke at 4-4 and had a chance to close it out.
Barty upped the aggression again and broke back to level the score, but couldn't consolidate, with Kvitova immediately breaking back.
Kvitova's second attempt at serving it out was worse than her first, sending one forehand metres wide and double faulting again.She ended the match with 10 double faults and 45 unforced errors, but was too good in the tiebreak, taking it 7-3.
Despite the loss, Barty will be confident heading into the Australian Open next week.
In Sydney, she defeated three players ranked higher than her, with world number one Simona Halep, Elise Mertens (12) and Kiki Bertens (9) all being knocked out by the Aussie.
She gets her campaign underway against Thailand's Luksika Kumkhum on Monday night.
She has a potential third round showdown with Jelena Ostapenko, who she defeated 6-3 6-3 in the first round in Sydney. Maria Sharapova and defending champion Caroline Wozniacki shape as possible fourth round opponents, with Kvitova, Andrea Petkovic and world number 11 Aryna Sabalenka all in the same quarter of the draw.
Kvitova will play Magdalena Rybarikova in the first round, with Petkovic, Barbora Strycova and Sydney International surprise package Yulia Putintseva all possible first-week opponents.
Earlier in the day, Alex de Minaur was too good for Gilles Simon in the pair's delayed semi-final, with the 19-year-old Aussie earning a spot in a second consecutive final against Andreas Seppi.
After persistent rain on Friday night, de Minaur was forced to play two matches in a day in sweltering Sydney conditions on Saturday.