Caroline Wozniacki battled through a troublesome knee complaint to earn a crucial three-set victory over Petra Kvitova in the White Group of the WTA Finals.
Defending champion Wozniacki and Kvitova lost their opening matches of the round-robin phase to crank up the importance of Tuesday's contest in Singapore.
It was Wozniacki who struck first in a tense opening set, but a problem with her left knee limited the Dane's movement and allowed Kvitova to level the match.
The see-saw nature of the match went back in Wozniacki's favour, though, and the second seed completed a 7-5 3-6 6-2 victory to end a four-match losing streak over Kvitova dating back to 2014.
Victory reignites Wozniacki's bid to reach the semi-finals, while Kvitova - who mixed 40 winners with as many unforced errors - will be eliminated should compatriot Karolina Pliskova beat Elina Svitolina.
It took until game eight for the first break of the match when Wozniacki followed up a fierce backhand with a thumping forehand winner.
The Dane failed to serve out the opener, wasting a set point in the process, as Kvitova hit back immediately and then earned another break-point chance in game 11.
That danger was quelled and, with Kvitova serving to stay in the set, Wozniacki saw another set point go missing before the third time proved a charm when the Czech put a forehand into the net.
After a break apiece to start the second, Kvitova stole in front again in game three when she correctly reviewed a ball called out and Wozniacki needed strapping on her knee during a medical timeout after game four.
A glorious deft lob briefly levelled the set at 3-3, but Kvitova quickly regained the advantage and, with Wozniacki's movement now clearly hindered, she cantered through the remaining games.
But Wozniacki gained a second wind as the momentum swung once again.
Wozniacki broke at the first time of asking with a double-backhand pass at the end of a majestic rally and, with Kvitova – who is asthmatic – visibly struggling with her breathing at a change of ends, a break of love followed to establish a 4-1 lead.
From there it was a formality for Wozniacki, who can now look ahead to her final group match with Elina Svitolina.
Wozniacki  bt Kvitova  7-5 3-6 6-2
Wozniacki - 19/14
Kvitova - 40/40
Wozniacki - 3/0
Kvitova - 2/3
BREAK POINTS WON
Wozniacki - 6/9
Kvitova - 5/13
FIRST SERVE PERCENTAGE
Wozniacki - 70
Kvitova - 59
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Wozniacki - 62/50
Kvitova - 51/55
Wozniacki - 96
Kvitova - 84
|Thunder frustrations continue against Renegades|
|Alonso vows to clear name in tax fraud case|
|Classy Nadal downs Tiafoe to set up Tsitsipas semi|
|Hoedt leaves Southampton for Celta Vigo on loan|
|Melbourne City 4 Western Sydney Wanderers 3: Hosts edge thriller with two goals in last six minutes|
|Wilder won´t even pick up the phone - Hearn not hopeful of AJ bout|
|Sala was on board missing plane, say French authorities|
|Arsenal´s Bellerin out for season with ACL rupture|
|Gatland waiting on ´concrete´ offers|
|Ronaldo accepts prison sentence and €18.8m fine for tax fraud|
|Tsitsipas: It was vital to back up Federer win|
|Awesome Kvitova ends Barty´s home run in Melbourne|
|CA rejects Thunder appeal for full points in abandoned Heat clash|
|Emiliano Sala: Concerns grow for Cardiff striker after plane goes missing|
|Harden unimpressed with refs in Rockets´ 76ers disappointment|
|Ronaldo arrives for sentencing in tax fraud case|
|Record-breaking evening ´one of those nights´ for Warriors star Thompson|
|Hazard still interested in Real Madrid but won´t rule out Chelsea stay|
|Collins moves past Pavlyuchenkova, into Australian Open semis|
|Kohli makes history with ICC awards sweep|
|Thompson sets NBA record with 10 straight made three-pointers to open game|
|76ers hand Rockets largest loss of season, Harden scores 37 points|
|Tsitsipas overcomes Bautista Agut to continue Aus Open run|
|Barcelona move a ´dream come true´ for Boateng|
|Rams coach McVay on Gurley: I´ve got to get him more opportunities|
|Butler´s sprained wrist not expected to keep him out ´long term´|
|Saints owner Benson will ´aggressively pursue changes in NFL policies´|
|Levante to take Copa case to CAS|
|It can happen – Allegri plays down Ronaldo penalty miss|
|Mavericks´ Doncic becomes second-youngest player to record triple-double|
|Yankees send Sonny Gray to Reds|
|Ashley Cole reunited with Frank Lampard at Derby County|
|Arnold ready to mix things up in 2019 Asian Cup quarter-finals|
|Arum: Joshua desperately needs to fight in the United States|
|South Korea v Bahrain: Bento optimistic of continuing unblemished campaign|
|Bolton Wanderers 0 West Brom 2: Baggies bounce up to third after tennis ball protest|
|Confident Moeen ready to shine for England in the Caribbean|
|Juventus 3 Chievo 0: Allegri´s men cruise despite Ronaldo penalty save|
|Boateng completes shock Barcelona switch|
|United Arab Emirates 3 Kyrgyzstan 2 (after extra time): Khalil penalty sets up Socceroos showdown|
|West Indies add Drakes to new-look coaching team|
|Barcelona is a huge opportunity – Boateng confirms shock move is close|
|Donnarumma wishes Higuain luck ahead of expected Chelsea switch|
|Qatar v Iraq: Katanec anticipating ´huge challenge´ in last 16|
|Nuno hit with FA misconduct charge for pitch celebration|
|Furious Carreno Busta and Zverev bow out, Djokovic marches on|
|#NotMartinFromWakefield – Siewert shows viral sensation the door|
|Djokovic feeling the strain after late-night Medvedev battle|
|Henderson sidelined again ahead of Six Nations|
|Australia 0 Uzbekistan 0 (aet, 4-2 on penalties): Ryan heroics see holders hobble onwards|
|Halep exit leaves four-way fight to be crowned number one at Australian Open|
|Super Bowl-bound Rams set for London return, Chiefs to face Chargers in Mexico|
|Huddersfield appoint Siewert as Wagner´s replacement|
|Genoa 0 AC Milan 2: Borini and Suso step up with Higuain left out|
|McTominay signs new Manchester United contract|
|Pizzi to stand down after Saudi Arabia elimination|
|Boateng closing in on shock Barcelona switch - reports|
|Catalans to defend Challenge Cup after resolving RFL dispute|
|Djokovic wears down Medvedev to reach last eight|
|Mouratoglou: I knew ´loyal´ Serena would not fire me after US Open turmoil|
|Barcelona B defender Wague accuses Ejea fans of racist abuse|
|I felt like I had been hit by a train - Halep upbeat despite losing Serena battle|
|Arsenal confirm Mislintat departure|
|Icardi will renew, 100 per cent - Wanda Nara offers latest Inter assurance|
|Japan 1 Saudi Arabia 0: Four-time winners send Pizzi´s men out|
|A souvlaki maybe named after him, a growing fan base – Tsitsipas creating Melbourne buzz|
|Barca winger Dembele out for 15 days|
|Strikers blown away by Hurricanes in Adelaide|
|Ireland lose Beirne for England and Scotland clashes|
|´Innate fighter´ Serena says character key to beating Halep|