TENNIS: ATP: Second seed Novak Djokovic overpowered seventh-seeded Argentine Juan Martin del Potro 7-5, 6-3 in the opening match of the Masters Cup yesterday in Shanghai, China.

In the day's second match, fourth seed Nikolay Davydenko defeated sixth seed Jo-Wilfried Tsonga 6-7, 6-4, 7-6 after fending off a dramatic comeback by the Frenchman in the third set before a roaring crowd.

Serb Djokovic broke del Potro's serve to claim the final game of the first set, and after a close start to the second came on strong with a succession of aces to win the final three games.

Djokovic said his experience from last year's Masters Cup - where he came away winless - helped him to fend off the aggressive del Potro, who is making his Masters debut.

"He made some unforced errors in the important moments, so I used my opportunities wisely," Djokovic said. "In important moments, I played my best tennis."

Del Potro (20), the youngest player at this year's €4 million Masters Cup, said he was already satisfied with his performance for the year and had gained confidence after winning four tournaments in a row and helping Argentina reach the Davis Cup final.

"I did a great season, so I don't expect any more for this year," he said.

Roger Federer is the top seed at the round-robin tournament, after world number one Rafael Nadal pulled out due to injury.

WTA: Venus Williams of the US beat Russia's Vera Zvonareva yesterday to win the year-end WTA Championship for the first time. Williams (28), ranked eighth, lost a first-set tiebreak before coming back for a 6-7 (5-7), 6-0, 6-2 victory in Doha, Qatar.

It's the 39th title of her career. She picked up a winner's check for €1 million.

"That was a hard-fought match, really every point right down to the end,'' Williams said. "Those last games, we were both wanting it so bad. I wanted it, I'm glad I got it!''