Shanghai - Novak Djokovic broke his duck at the Masters Cup, winning his first career match at the season wrap-up after three 2007 losses.

The Serb overpowered Argentine Juan Del Potro 7-5, 6-3 to take the early lead in the Gold group.

"I'm happy to win, that's for sure, I'm satisfied," said Australian Open champion Dokovic.

"I played really well from the start and felt good on the court. But then suddenly I just lost momentum and started serving really badly.

"He got back to the game. It was my fault, but I played well in the important moments. I'm happy to get through in straight sets."