Caroline Wozniacki booked her place in the semi-finals of the WTA Finals with another thumping win while Caroline Garcia staged a great comeback to keep her hopes alive.
Wozniacki began her campaign in the Red Group by dropping just two games against Elina Svitolina and was in similarly destructive form in a 6-0 6-2 victory over world number one Simona Halep.
Garcia, whose stunning form this autumn catapulted her into the tournament at the last minute, lost her opening match to Halep and looked to be heading out when she trailed Svitolina 3-5 in the deciding set.
But the Frenchwoman reeled off the final four games to win 6-7 (7/9) 6-3 7-5 and secure a debut victory.
All three women have a chance of joining Wozniacki in the last four, with Halep in the marginally stronger position.
Garcia must beat Wozniacki and hope Halep is defeated by Svitolina, while the Ukrainian needs a straight-sets win and for Garcia to lose.
Halep had looked in fine form in her win over Garcia but could not find her rhythm against Wozniacki, who raced through the first set in just 24 minutes.
The second was more competitive but Halep struggled to contain both the brilliance of her opponent and her own negativity and succumbed rather meekly.
Wozniacki told BT Sport: "I felt like I played very well. Obviously she got frustrated and I felt like I was doing everything just a little bit better.
"I feel like I'm back where I'm supposed to be. It's been a great year for me and I'm finishing it off in style."
The defeat was a blow to Halep's hopes of finishing the year ranked number one, and she said on wtatennis.com: "I think it was one of my bad days. I made too many mistakes and she didn't miss."
Svitolina and Garcia's match lasted more than twice as long as the one that preceded it and was the second dramatic encounter between the pair this month.
Garcia would not be in Singapore had she not saved a match point against Svitolina on her way to winning a second successive title at the China Open.
This was another topsy-turvy encounter, with Svitolina saving two set points in the opening tie-break. Garcia appeared to be in tears as she spoke to her father, who is her coach, at one change of ends but she recovered to win the second set.
Svitolina then looked to have a decisive advantage but, as in Beijing, Garcia proved the stronger in the end.
The 24-year-old said: "I'm very happy about the fight I showed on court. It was very difficult, a lot of emotion, some up and down, but at the end I could control myself better than she did."