Simona Halep was pleased to execute her game plan to perfection as she opened her WTA Finals campaign with a straight-sets victory over Madison Keys in Singapore.

The world number four only needed 69 minutes to dispatch her American opponent in the first contest of the round-robin stage, Halep cruising to a 6-2 6-4 victory to maintain a 100 per cent record from four matches against Keys in 2016.

Halep quickly wrestled momentum away from Keys in the opening set, and a coaching timeout in the second was unable to help the Finals debutant turn things around as her opponent turned the screw.

Unforced errors ultimately cost Keys but for Halep it was the perfect start as she looks to avenge her group stage elimination 12 months ago.

"I felt very well on court today," she said after the Red Group match. "It was better that I knew her. I played few times this year. I won every time, so I had an advantage.

"But still I played a good tennis. I think I played exactly what I had to play against her. I was focused, everything went as I wanted, so I'm happy with the way that I played.

"I could manoeuvre the game as I wanted. The ball is staying low here, so I think fits me. It's good that I can be strong on my legs."

Keys blamed nerves on her disappointing performance but hopes to improve as she looks to escape the group shared with Angelique Kerber and Dominika Cibulkova.

"I just think having a match under my belt there is a little bit less nerves going out next time and I can go and play with nothing to lose," Keys noted in her post-match press conference.

"But I think I the biggest thing is just being excited that I getting to out and play another match here."

STATISTICAL BREAKDOWN

Halep [3] bt Keys [6] 6-2 6-4

WINNERS/UNFORCED ERRORS 

Halep - 5/12
Keys - 16/41

ACES 

Halep - 0
Keys - 1

BREAK POINTS WON 

Halep - 4/10
Keys - 1/2

FIRST SERVE PERCENTAGE 

Halep - 59
Keys - 59

PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE 

Halep - 72/68
Keys - 58/39

TOTAL POINTS 

Halep - 66
Keys - 44