By John O'Brien
SINGAPORE (Reuters) - Romania's Simona Halep kicked off her campaign for a maiden WTA Finals title in emphatic fashion with a thumping 6-0 6-3 victory over U.S. Open champion Flavia Pennetta in the opening match of the eight-woman season-ending tournament on Sunday.
The world number two is the highest ranked player in the field after Serena Williams, who has won the tournament the last three years, withdrew citing the need to rest after a year spent carrying injuries.
Halep crushed Williams in round robin play a year ago before losing to the American in the final and her love of the Singapore Indoor Stadium hard court was evident in a first set she wrapped up in 26 minutes after breaking serve three times.
The Romanian had arrived in Singapore under an injury cloud after picking up an ankle knock at the start of October, but the 24-year-old moved effortlessly around the court on Sunday and withstood Pennetta's attempts to get back into the contest.
The 33-year-old Italian played more like she had on her way to a stunning victory in New York last month in the second set but her resistance ended in a marathon eighth game when she dropped serve to trail 5-3 after staving off three break points.
Pennetta, who announced she would retire from tennis at the end of the season, forced only two break points, both in the opening game of the second set, during the entire match and her unforced error count of 27 made life much easier for Halep.
"I am so happy to be back in Singapore and glad that I was able to play really well today," Halep said in a courtside interview.
Round robin play continues later on Sunday when world number three Maria Sharapova takes on Agnieszka Radwanska in a contest between the other two players in the 'Red Group'.
The 'White Group' consists of Garbine Muguruza, Petra Kvitova, Angelique Kerber and Lucie Safarova.
(Editing by Peter Rutherford)