SINGAPORE - Top seed Simona Halep looked completely at ease on Sunday afternoon in a ruthless 6-0, 6-3 victory over Flavia Pennetta in her opening match of the BNP Paribas WTA Finals Singapore presented by SC Global.

Halep, the world No. 2 women's tennis player, was the runner-up last year to Serena Williams, who is not competing this year.

Said the Romanian, who had an inferior 1-4 record against her Italian opponent before the match: "I played fast, I played smart and aggressive. I was enjoying the match. I'm really happy to be back here and I really wanted to thank (the fans) for coming."

Pennetta, the reigning US Open champion, was undone by a slew of 27 unforced errors, and also failed to capitalise on her two chances to break.

Meanwhile, in the other Red Group singles tie of the day, Maria Sharapova overcame Agnieszka Radwanska 4-6, 6-3, 6-4 in a battle that took two hours and 47 minutes.

It was Sharapova's first complete match since July, having been plagued by both leg and arm injuries.

She said: "This is my first completed match since July. It's a pretty big deal for me. I'm so happy I got through and have a chance to play two more matches, hopefully more. I couldn't be happier."

In the WTA Rising Stars Invitational tournament, Japan's Naomi Osaka made a stunning comeback when she saved four championship points against France's Caroline Garcia to win 3-5, 5-4, 4-1.