After midnight, Marie Bouzkova completed her first top 100 win and ruined Sam Stosur's 1000th career match in a contest that technically spanned two years. The world No.139 showed a fantastic performance as she came back to claim her biggest win in three sets.
She demonstrated a emarkable composure and shot-making all night, winning 80% of first serve points and hitting 29 winners against the Australian, who won just four matches in her career in the tournament.Bouzkova will play her compatriot Karolina Pliskova in her first ever top 10 clash.
Gold Coaster Kim Birrell pulled off the first big upset of Brisbane International 2019, grinding out a 57 64 76(5) victory over No.7 seed Daria Kasatkina. Brisbane International champion Karolina Pliskova battled back from the brink against fiery Kazakh Yulia Putintseva, edging through, 4-6, 6-3, 6-4 to reach the second round.
Also Bertens and Kontaveit in different manners moved to the second round. Playing before a packed Show Court 1 and watched on by the likes of her compatriots Lleyton Hewitt and Jordan Thompson, Birrell fought back from 3-5 down in the third set to post her first win over a top-10 opponent, 5-7 6-4 7-6(5), after three hours and eight minutes.
"I'm on a massive high at the moment... I can't put it into words," said a non-stop-smiling Birrell who will now face Lesia Tsurenko. ""There were so many familiar faces in the crowd... it felt really special to get this win in front of so many people I know".
Moments before Birrell’s breakthrough, fellow Aussie Destanee Aiava took down Kristina Mladenovic 6-4 7-6(3) on Show Court 2. The young Australian made a stunning debut here two years ago, as she reached the second round as a qualifier losing to Svetlana Kuznetsova.
Birrell, a former Australian Open junior semifinals, underwent a career-threatening elbow surgery in 2016, and had to grind away on the ITF circuit since her comeback in February 2017. Earlier this month, she won the Australian Open Wildcard Playoff to earn a spot in the main draw of her home Slam.
""I think I owed it to myself, first and foremost. I owed it to my coach, my family, and Tennis Australia for giving me the opportunity to play. I knew that I've been playing good tennis. I definitely believed in myself, sure," she admitted, WTAtennis.com reported.
"I think you definitely can't beat yourself before walking out on to the court or there's no point in walking through that gate". The 18-year-old will meet second seed Naomi Osaka in the second round. "This past week I've been mistaken for Naomi about four times, so we'll see if they can tell us apart when we play," she told reporters.
"I'm looking forward to the experience." Pliskova needed to recover from a set and a break down to dismiss Putintseva, whom she had outlasted in the first round en route to the title two years ago. The Czech called down coach Rennae Stubbs early in the second set, and began a crucial five-game winning streak.
Stubbs and Conchita Martinez, confirmed as full time coaches in her team, both wanted her to improve her legs. "I don't understand, because I feel like they're great! It's about the movement, which could be better, and off-court fitness" she joked as WTAtennis.com quoted her to say.
Awaiting Pliskova in the second round is either qualifier Marie Bouzkova or 2011 US Open champion Samantha Stosur, who took a wildcard into Brisbane and played her 1000th overall match in her career. Kiki Bertens needed three sets to defeat 62 67(6) 64 Elise Mertens.
Making her second main draw appearance at Brisbane International, having fallen in the first round in 2018 to Konjuh, Bertems completed her 24th career Top 20 victory as she beat the Belgian for the first time. Starting 2019 season ranked at a career-high No.9, Bertens completed two breaks in the last two return games of the first set to seal it, showing a more assured strategy from the baseline.
Mertens, more inconsistent off both sides, suddenly found drive and depth and opened the second set with two successive breaks. Her new coach David Taylor often asked her to be more aggressive in return and hit flat crosscourt backhands to expose the Dutch on her weaker side.
Bertens levelled from 0-3 to 4-4 but Mertens won the 18th of 36 tiebreaks played at WTA main draw level as she converted the second set point. The Belgian, on her main draw debut at Brisbane International, aimed to seal the fourth career Top 10 win, having previously beaten No.10 Cibulkova (2017 Beijing), No.4 Svitolina (2018 Australian Open) and No.3 Stephens (2018 Cincinnati).
Her past successes over today's opponent augured well for her prospects at the tournament: she beat the Dutchwoman en route to her maiden career title at 2017 Hobart and her first Premier-level semifinals showing at 2017 New Haven.
But, after an exchange of breaks in the first two games, Mertens played her worst service game to gift Bertens the chance to serve for the match at 5-4. And the Dutch completed her 155th main draw victory. Anett Kontaveit won the first nine games of the match and claimed an easy 60 63 win over former semifinalist Carla Suarez Navarro, who never beat a top-30 opponent in the tournament's history.
Kontaveit, starting the season at No.21, had served for the match at 5-4 in the final set before losing to the Spaniard in their previous match in the fourth round at 2018 Australian Open. Today, she was extremely focused and aggressive on serve and return from the opening stages.
Quickly, she established as the best player on court and sealed thee 79th main draw win to move to the second round for the second straight season.
WTA Brisbane - First round
 Karolina Pliskova (CZE) d. Yulia Putintseva (KAZ) 4-6, 6-3, 6-4
 Kiki Bertens (NED) d. Elise Mertens (BEL) 6-2, 6-7(8), 6-4
[Q] Marie Bouzkova (RTC) d. [WC] Samantha Stosur (AUS) 4-6, 6-2, 6-2
[WC] Kimberly Birrell (AUS) d.  Daria Kasatkina (RUS) 5-7, 6-4, 7-6(3)
[Q] Harriet Dart (GBR) d. [WC] Priscilla Hon (AUS) 1-6, 6-3, 6-4
Anett Kontaveit (EST) d. Carla Suárez Navarro (ESP) 6-0, 6-3
Lesia Tsurenko (UKR) d. Mihaela Buzarnescu (ROU) 6-0, 6-4
[Q] Destanee Aiava (AUS) d. Kristina Mladenovic (FRA) 6-3, 7-6(2)
Donna Vekic (CRO) d. Magdalena Rybarikova (SVK) 6-1, 6-2