BEIJING - World No. 1 Novak Djokovic of Serbia fought off tough resistance from Spaniard Fernando Verdasco in the second round to reach the quarterfinals of the China Open on Thursday.

The Serb overcame a second slump to beat Verdasco 7-5, 2-6, 6-2 in one hour and 54 minutes. With the victory, the three-times winner in Beijing has improved to a 16-0 mark at the ATP World Tour 500 hard-court tournament.

He must retain his title this week to keep a chance of holding his top spot for a 102nd week. If No. 2 seed Rafael Nadal reaches the final, he will reclaim the No. 1 ranking regardless of Djokovic's results.

The 26-year-old Djokovic squandered a 4-2 lead in the first set, but broke Verdasco again in the 12th game to seal the opener.

However, Verdasco fought back strongly. The former World No. 7 broke Djokovic in the third and seventh games to level the match and force a decider.

Djokovic made a strong start in the third set, opening up a 2-0 lead, and saved a break point in the seventh game before closing out victory.

Australian Open champion Djokovic is bidding to win his first title since the Monte-Carlo Rolex Masters in April, when he dethroned eight-time champion Nadal in the final.