WTA Finals: Angelique Kerber beats Dominika Cibulkova, Simona Halep dominates Madison Keys

World No. 1 Angelique Kerber closed out the opening night of the BNP Paribas WTA Finals with a thrilling 7-6 (5), 2-6, 6-3 victory over No. 8 seed Dominika Cibulkova in Singapore on Sunday.

Kerber is 1-0 in the Red group of round robin match play along with Simona Halep, who handled Madison Keys 6-2, 6-4 earlier in the day.

Kerber had to work much harder, needing two hours and 17 to get past Cibulkova, who had won the past four meetings between the two in straight sets.

"It was for sure a little bit better than the last match I played here against (Lucie) Safarova last year, but it's always tough to play the first matches here," Kerber said after the match.

"Of course the pressure is not really big for me, but it's a new situation."

In pushing Kerber to three sets, Cibulkova sits ahead of Keys in the Red group despite the loss.

"In this game it's all about the small details, and she was a bit more consistent in some games and that's what made her win today," Cibulkova said.

"I have my first match already behind me, and I know I'll be ready for my second one. It makes a difference to know I'm not leaving tomorrow. "

Halep opened the day with a dominating victory over Keys, who struggled in committing 41 unforced errors against 16 winners in her first WTA Finals match.

"I just think having a match under my belt there is a little bit less nerves going out next time and I can go and play with nothing to lose," Keys said.

"But I think I the biggest thing is just being excited that I getting to out and play another match here."

The White group begins its round robin play on Monday, with Agnieszka Radwanska facing Svetlana Kuznetsova and Karolina Pliskova facing Garbine Muguruza. Kuznetsova is coming off a title at the Kremlin Open.