Novak Djokovic improved his perfect record at the China Open to 25-0 by beating Simone Bolelli of Italy 6-1, 6-1 Tuesday in the first round.
The top-seeded Djokovic's winning streak started in 2009, when he won the first of his five titles at the tournament. He has dropped only three sets out of 51 in his five appearances. He didn't play in 2011.
Besides singles, Djokovic is also teaming with younger brother Djordje in doubles for the first time at an ATP Tour event.
Rafael Nadal also advanced to the second round, beating Chinese wild-card entry Wu Di 6-4, 6-4. Nadal dropped serve four times in the match, including three straight games in the second set.
The third-seeded Nadal is in the uncharacteristic position of needing a strong finish to the season to qualify for the ATP Finals in London next month.
The Spaniard looked to be cruising against the No. 230-ranked Wu, playing his first top-10 opponent, when he broke to take a 1-0 lead in the second set. But Wu broke right back, and then twice more before Nadal was finally able to serve it out.
''I think I played little bit too ... far away from the baseline,'' Nadal said. ''The last three games of the match I was playing better. I hit some good forehands down the line and that's why I finished well.''
On the women's side, U.S. Open champion Flavia Pennetta of Italy rallied to advance to the third round with a 3-6, 6-0, 6-4 win over Teliana Pereira of Brazil.
Also, eighth-seeded Caroline Wozniacki of Denmark defeated Chinese wild-card entry Wang Qiang 7-5, 6-0, and 10th-seeded Angelique Kerber of Germany beat Dominika Cibulkova of Slovakia 6-1, 6-4.
For the second straight day, the pollution in Beijing reached hazardous levels, according to the U.S. Embassy's real-time air quality index.
''The pollution, I think we're used to it when we play here,'' Wozniacki said. ''You know, we just play. We just play.''
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