Serena Williams shook off the rust and a feisty challenge from Serbia’s Ana Ivanovic to open the defence of her WTA Finals title with a 6-4 6-4 victory in the opening match of the elite eight-player tournament yesterday.

In the second match, Romania’s Simona Halep joined Williams at the top of the Red Group standings after the world number four brushed aside Canada’s Eugenie Bouchard 6-2 6-3 on the purple hardcourt at Singapore’s Indoor Stadium.

Bouchard, 20, could barely find the court with her attempted winners as Halep continued to hound her at every opportunity and it was somewhat fitting that a double fault on match point handed victory to the Romanian.

Illness and a knee problem forced the American world number one to withdraw from her last two tournaments since winning a third straight US Open title last month and Williams struggled early in an arena hosting the event for a first time.

First service

Pre-match pyrotechnics left the Indoor Stadium looking as hazy as the city-state’s streets on a polluted day but once the smoke had cleared, Williams was forced to dig deep in her first service game before putting the pressure back on Ivanovic, who surrendered the set after going close to take a 5-4 lead.

The pair traded breaks to open the second set and then raced through their service games until Williams made the vital breakthrough in the 10th game with a series of thunderous forehands before an Ivanovic error handed the contest to her opponent on her first match point.

“I am really excited with how I played tonight. I have been working hard all my life for nights like this and I love it. So thank you for coming tonight,” Williams said.

“I was fighting as hard as I could and I think I am losing my voice from all of those ‘come ons’ I was shouting.”

The victory was Williams’ 16th in a row at the tournament as the 33-year-old American remains on course for a hat-trick of titles as she attempts to retain a no.1 ranking under threat from Maria Sharapova this week.