Djokovic outclasses Del Potro in Masters opener

SHANGHAI (Reuters) - Second seed Novak Djokovic overpowered seventh-seeded Argentine Juan Martin del Potro 7-5 6-3 in the opening match of the Masters Cup on Sunday.

In the day's second match, fourth-seeded 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 told a news conference. "In important moments, I played my best tennis."

Del Potro, 20, the youngest player at this year's $4.55 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 week-long round-robin tournament, after world number one Rafael Nadal pulled out due to injury. Federer is seeking to become only the third player to claim five season-ender victories.

Frenchman Tsonga, down 5-2 in the third set, battled back from match point to win three successive games but then came away pointless in the tiebreak.

"When I came back I played very, very well. I gave everything on every ball and Nikolay today was just better than me," he said.

"Like we saw at the tiebreak, he was better physically and that's it," he added, placing some of the blame for his disappointing finale on a lack of energy -- due in part to having to chase after his own towels.

He also expressed gratitude to the cheering crowd. "Of course they helped me," he said. "You need the crowd to cheer with you."

Davydenko credited his victory in part to steady nerves.

"I was from the beginning until last point feeling the same. Just I was not nervous," said the Russian. "I think Tsonga in the tiebreak was already a completely different guy."

(Editing by Sonia Oxley)