Bertens feared she did not belong in Kerber clash

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."