Tennis: Serena takes out Billie Jean trophy

Serena Williams of the US holds her trophy aloft after defeating Romania's Simona Halep in the singles final at the WTA tennis finals in Singapore. Photo / AP

The lead-up to yesterday's championship match at the WTA Finals suggested Serena Williams would face a major challenge to beat Simona Halep, but then, the No. 1-ranked player has made a career out of performing at her best when it matters most.

She did it again in Singapore, dispatching Halep 6-3, 6-0 just four days after a group-stage game between the pair in which the Romanian player dropped only two games and handed Williams her heaviest defeat for 16 years.

Coming into the tournament after having to withdraw from the China Open and Wuhan Open with illness and a knee injury, and just a day after a gruelling three-set classic against Caroline Wozniacki, there were plenty of reasons to believe the 33-year-old could be vulnerable.

The doubts were quickly swept aside as Williams overpowered her opponent in an imperious performance.

She won 11 of the last 12 games in the match to join Martina Navratilova and Steffi Graf as the only players to have won five titles in the season-ending championships.

"I just started training, because I had such a bad knee in Beijing I didn't know if I'd be able to play here, and now I have won the Billie Jean King trophy - I am so excited," Williams said.

Williams changed her approach from the group-stage contest, attacking Halep's second serve with fierce ground strokes, and regularly rushing the net to cut the points short and prevent her opponent from playing her preferred style.

"I had to play more Serena-style tennis and just do what I do best," Williams said.

"I was expecting a much better player than I was in the earlier round. Being ready for that really was able to help me out."

Halep's run in this tournament capped a remarkable rise, having gone from No. 64 in the rankings to No.4 in the course of 17 months, with a French Open final appearance along the way.

However, her relative lack of experience of big occasions compared to the 18-time Grand Slam champion proved telling.

"I was nervous before the match that I had to play this big final," Halep said. "I couldn't manage very well the situation.

"I knew that she would be more motivated during this match because we played a few days ago and I won."

Halep's victory in the group stage ended Williams' 16-game winning streak at the WTA Finals.