Bertens feared she did not belong in Kerber clash

Thrashed in the first set and trailing in the second, Kiki Bertens feared she was out of her depth before beating Angelique Kerber.

Kiki Bertens during the clash against Angelique Kerber in Singapore.

Kiki Bertens questioned if she was cut out for the WTA Finals when she trailed Angelique Kerber before staging a spectacular comeback.

The world number nine - in Singapore after an injury to Simona Halep - was a set and a break down to top seed Kerber at one stage, with the Wimbledon champion seemingly set for a comprehensive opening victory.

But a remarkable turnaround saw Bertens come storming back to clinch a 1-6 6-3 6-4 victory, gaining a foothold at the season-ending tournament.

"In the beginning when you play like this, I was really thinking, 'OK, do I belong here? I'm playing so bad,' and all that kind of stuff," said Bertens.

"At the beginning of the second, it was just like hopefully I can get a few more games. I was really playing not good, stressing a little bit too much, thinking about playing bad.

"I think one thing I can be really proud of is that I turned that match around, that I played more aggressive, going a little bit out of my comfort zone to get a win.

"I'll do everything to win here and that's what we're going to do for the next match. Hopefully I feel good then - I was fist pumping so much that I got some cramps in the arm.

"Maybe [I feel] not great, but it was just really exciting to win this match. I think there was a lot of stress during the match, so maybe not too good for the body."