SINGAPORE - Ten games into her round robin clash with top seed Angelique Kerber, Kiki Bertens admitted the doubts were starting to sink in at the BNP Paribas WTA Finals Singapore presented by SC Global.

“In the beginning when you play like this, I was really thinking, ‘Okay, do I belong here? I'm playing so bad and all that kind of stuff,’” she recalled when she fell behind a set and 2-0 to the reigning Wimbledon winner.

Though Bertens was a last-minute addition to the Elite Eight after Roland Garros champion Simona Halep was forced to withdraw, her runner-up finish at the Mutua Madrid Open and title run at the Western & Southern Open - where she saved a match point to beat Halep in the final - made her more than a worthy contender at the Singapore Indoor Stadium.

Still, the stressful six weeks the Dutch star spent in search of a qualification berth seemed to have taken its toll.

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

- Kiki Bertens

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

Bertens consulted longtime coach Raemon Sluiter, who famously gave his charge an ultimatum at this tournament last year: commit 100% to the sport or step away from the game.

“I said, ‘Well, if we continue like this, this is it for me, and I strongly advise you to go and do something else. Because I have seen you over the last four or five months. The only times I saw you smile were at home and never when we are on tour. You're making good money. But it's not bringing you anything apart from that. And no money is worth feeling miserable all the time,’” he recalled during a coaches press conference on Monday.

Bertens responded by outlining her goals for the upcoming 2018 season, and surely fulfilled most of them in the ensuing months, winning two titles, earning career-best results at three of the four major events, and securing a spot in the Top 10.

She used much of that same mettle to turn the tide against Kerber, winning six of the next seven games to level the match and navigate a tricky decider to serve out a first win in her WTA Finals debut.

“Before the match the plan to try to play aggressively where I can but not rush too much: play the rally and see how it goes.

“I called him already in the first set, and then more the plan was just hang in there, try to be tough, play some more rallies and then see. But I was making so many mistakes, so that didn't work out.

“In the third one, it finally worked better, and that was like to play more aggressive and go for my shots.”

Though she finished the match with 45 unforced errors, the 33 winners she hit more than made up the difference as she continued to play better on key points. Serving late in the third set, she dug out of a 0-40 deficit to consolidate her lead en route to victory.

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

“I’ll do everything to win here, and that's what we're gonna do for the next match, and hopefully I feel good then.”

Finishing up press a little before 1:30AM local time, the No.8 seed sheepishly admitted to one injury she’s sure will heal in time for a meeting with 2017 US Open champion Sloane Stephens.

“I was fist pumping so much that I got some cramps in the arm! Maybe 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.

“Tomorrow is a day to recover, so that's great. And then I will be ready again on Wednesday.”