As the ball from Madison Keys' racket sailed long, setting up two break points for Simona Halep yesterday, a fan in the stands at the Singapore Indoor Stadium remarked: "Halep is very consistent."

And he was right, for it was consistency that gave the world No. 4 the confidence to rip a backhand passing shot to win the ninth game of the second set.

It was also consistency that gave the Romanian her first victory of this year's BNP Paribas WTA Finals Singapore presented by SC Global.

Halep, making her third consecutive appearance here, overcame big-hitting Keys' flat shots and sharp angles to prevail 6-2, 6-4 .

Asked about the backhand winner that gave her the break and left Keys staring helplessly as the ball passed her, Halep grinned.

Nodding, she said: "It was nice."

The 25-year-old had earlier responded to a Keys drop shot by deftly returning the ball cross-court for a winner, and she added: "(The drop shot) was amazing. I didn't think about anything else; just that shot. Then for the backhand I said, 'Oh I feel it.' It was good for me because I was confident it would work. My backhand is my best shot, so it has to work."

It was Halep's fourth win over the American this year. And while she admitted that her head-to-head record (4-1 before yesterday's match) against Keys gave her some confidence, she knows she played well yesterday. Revealing that she had "panicked a little bit" after missing some easy shots, Halep added: "I know she can play some amazing shots and also miss easy shots, because that's her game - she goes for everything.

"I stayed there; I think I did a good job. I was positive until the end. My serve helped me a lot today."

The 2014 finalist here won 72 per cent of her first-serve points and 68 per cent of her second-serve points, while Keys recorded 58 per cent and 39 per cent, respectively.

Halep cruised through the first set, sending the balls high and deep to counter debutante Keys' flat shots. A slew of unforced errors from the American saw Halep reel off five straight games to take the first set 6-2.

The second set was a tighter affair, with both players exchanging breaks of serve to lock the score at 4-4 before Halep pulled away for the win.

World No. 7 Keys said: "(Halep) gets a lot of balls back; one of her strengths is making you feel like you have to go for more and take the risk. I think sometimes she makes me uncomfortable and I back away from playing my game and start going for things in a way that I shouldn't - that's something I'm going to have to work on."

The 21-year-old hit a total of 41 unforced errors to Halep's 12 but remained upbeat despite her loss, adding that she is excited to play her next match - against world No. 8 Dominika Cibulkova.

She said: "This is kind of a unique situation where I get to take the things that I liked and the things I didn't like, and move on.

"I think by just having a match under my belt, there is a little less nerves going out the next time, and I can play with nothing to lose."