SINGAPORE - The Red Group was back in action at the WTA Finals on Thursday and when the dust settled, it was Angelique Kerber and Dominika Cibulkova who advanced to the final four.

In the first match, Cibulkova defeated Simona Halep 6-3, 7-6, logging her first win at the event.

Playing with a purpose, the Slovakian was fast out of the gate as she gained an early break in the first set. She kept the pressure on the world no. 4, who played with heavy tape on her knee. Grinding point after point, Cibulkova never faced a break point in a strong opening set.

In the second set, both players struggled to hold serve as each broke their opponent three times. But despite efforts by the Romanian, Cibulkova dictated play and maintained her aggressive style throughout a set that would ultimately be decided by a tiebreak.

Cibulkova kept the pressure on Halep in the tiebreak but to the credit of the 25-year old, she would battle back gaining a 5-4 lead. However, it was Cibulkova who closed strong winning the final three points and the match.

“This win is really, really big for me,” Cibulkova said. “I feel relieved. I'm 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. It's just a great feeling 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.”

Later, Kerber met Madison Keys and by virtue of the results from the first match, the world no. 1 had clinched a spot in the semifinals before striking her first shot. Meanwhile, the American would need to win a set against Kerber to break the tie with Cibulkova and advance. She would not as the German cruised to a 6-3, 6-3 victory.

In the first set, Kerber took advantage of a difficult day serving by Keys, as she broke four times. And while she lost her serve twice in the set, Kerber was the most consistent from the baseline.

The frustrations continued in the second set for Keys who lost her serve twice while Kerber took advantage of numerous unforced errors to close out the set and match.

Keys finished with 31 unforced errors to go with just 15 winners while the steady Kerber only yielded 12 errors as she counter-punched her way to the win.

Kerber emphasized the importance of winning the match despite the knowledge that she had clinched a berth in the semifinals. “Today I wasn't thinking that I already was in the semis. It was important to go out to win the match and win all three matches,” she said.  “Now I'm going to the semis with three really good matches which gives me a lot of confidence.”

The White Group will be back on court Friday as Agnieszka Radwanska and Karolina Pliskova will face off with a spot in the semifinals on the line.