American Sloane Stephens weathered a Kiki Bertens storm to stay on course for the semi-finals in Singapore.
Sloane Stephens stands on the brink of the last four at the WTA Finals after coming out on top in an almighty battle with Kiki Bertens.
Bertens would have qualified for the semi-finals with a victory after Angelique Kerber beat Naomi Osaka in the first match in Singapore on Wednesday.
Yet Stephens ensured it is all to play for in the Red Group with one round-robin match remaining by coming from a break down in the final set to win 7-6 (7-4) 2-6 6-3.
Both debutants won their first-ever contests in the season-ending tournament and still have their fate in their own heads, with group leader Stephens facing Kerber on Friday and Bertens up against Osaka.
Defeats Bertens 7-6(4), 2-6, 6-3! pic.twitter.com/x3tlBfFMTG
— WTA (@WTA) October 24, 2018
Stephens knew a straight-sets win would put her through and the 2017 US Open champion got off to a great start, breaking when Bertens missed an inside-out forehand as she breezed into a 3-0 lead.
Bertens warmed to the task, mixing up her approach and forcing mistakes from the American, who was broken for a second time after taking a 4-2 lead.
It was Bertens coughing up the unforced errors in the tie-break, though, another uncontrolled inside-out forehand giving Stephens the opening set.
The eighth seed responded by winning the first two games of the second and led 5-1 as Stephens failed to contain the world number nine, who broke again to take it to a deciding set.
Stephens hung in there and won four consecutive games from 2-0 down in the final set, Bertens running out of steam as the fifth seed took control, sealing victory with a deft drop shot.
Stephens  bt Bertens  7-6 (7-4) 2-6 6-3
Stephens – 18/37
Bertens – 24/47
Stephens – 0/3
Bertens – 2/8
BREAK POINTS WON
Stephens – 7/13
Bertens – 7/9
FIRST SERVE PERCENTAGE
Stephens – 78
Bertens – 61
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Stephens – 50/47
Bertens – 66/34
Stephens – 92
Bertens – 101