Bertens, a last-minute replacement for the injured world No. 1 Simona Halep, continued her remarkable improvement this season by advancing into the final four as her opponent, US Open champion and crowd favourite Naomi Osaka, retired with an injured left hamstring after losing the first set 6-3. "It's going to bring me lots of confidence".
The encounter possessed a litany of scintillating rallies, as both players exhibited the combination of groundstroke prowess and unimpeachable movement which had pulled each of them through to the final after undefeated round-robin play and challenging three-set semifinal fights.
"That's how life can go sometimes, " said Bertens, who has beaten 12 top-10 players this season.
'It's never easy or never nice to win a match like this, but it is what it is, ' she said in a press conference after the match, according to the WTA.
2018 marks the first season she has reached four finals in a year, at Miami, Roland Garros, Montreal and now the WTA Finals (she previously reached three in 2016, at Auckland, Acapulco, Charleston, winning all three).
"To be at the last four, last tournament of the year, it´s unbelievable".
This year's final remained undefeated in the round robin stage, the 20th and 21st occasion a player has posted a ideal 3-0 record.
Despite her defeat, Stephens said: "My first time in Singapore was incredible".
Serving for her place in the final, Svitolina saved two break points before shutting Bertens down.
Stephens, making her debut at the WTA Finals, surrendered her serve again on a first match point for Svitolina in the eighth game by sending a backhand crosscourt wide. Stephens needed to work hard to hold to 5-2 as Svitolina earned further two break point chances in that seventh game.
Ukraine's Elina Svitolina celebrates after winning her semi final match againast Netherlands' Kiki Bertens.
Stephens' blistering forehand dictated, as she ran away with the first set. "I was very proud of my effort today".
There was no looking back for Svitolina, who defended solidly and attacked when she could.
The match started tensely, with Kerber unable to convert seven break points in Stephens´ first three service games, and the missed opportunities proved costly.
A confident Elina Svitolina used a more assertive approach to produce a "statement" WTA Finals triumph in Singapore on Sunday, as the Ukrainian eyes elusive Grand Slam success next year.
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