WTA Finals: Angelique Kerber and Dominika Cibulkova through to semi-finals in Singapore

Cibulkova beat Simona Halep 6-3 7-6 (7/5) before Kerber eased past Madison Keys 6-3 6-3

Kerber in action at the WTA Finals in Singapore (Getty)

Angelique Kerber posted her third straight win at the WTA Finals while Dominika Cibulkova seized her last chance to join the world number one in the semi-finals.

After losing her opening two matches, Cibulkova knew only a straight-sets win over Simona Halep and the same result for Kerber against Madison Keys would be enough to see her progress in Singapore.

And that is exactly what transpired, with Cibulkova winning a hard-fought match 6-3 7-6 (7/5) before Kerber eased passed Keys 6-3 6-3.

Halep had her left knee heavily strapped and was clearly in some discomfort but, knowing she needed a set to keep her hopes alive, she battled manfully to force a decider.

However, it was Slovakian seventh seed Cibulkova who won the second-set tie-break and the match.

The 27-year-old told a press conference: "This win is really, really big for me. I feel relieved. I'm really, really happy about my win, about the way I played and the way I handled the situation and the pressure.

"It seems like I'm playing my best tennis under the biggest pressure. To beat Simona in two sets - knowing that if I want to go further in the tournament, I have to beat her in two sets. That made me even stronger in the second set."

The result meant Kerber qualified for the semi-finals but she needed to beat Keys to secure top spot in the Red Group, while a set for the American would have sent her through instead of Cibulkova.

But the consistency of Kerber proved too much for debutante Keys, who dropped serve six times, winning just four of 20 points on her second serve.

In the semi-finals, Cibulkova will face White Group winner Svetlana Kuznetsova while Kerber will take on the winner of Friday's clash between Agnieszka Radwanska and Karolina Pliskova.