BEIJING, Oct. 3 (Xinhua) -- 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.
"Lack of concentration from my side. I had some chances in the start of the second set, and I managed to allow him to come back to the match and start playing well," Djokovic said of his slow start to the match.
"The important thing is that in the third set I regained the focus and the patience also, decreased the unforced errors, and managed to get a win, which is what counts in the end."
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.
Djokovic goes on to face Sam Querrey, who upset sixth seed Stanislas Wawrinka Switzerland 6-3, 7-6(2) in 76 minutes.
The American fired 11 aces and converted three of his four break points to record his first win in four attempts against Wawrinka, who is currently eighth in the ATP Race To London.
There's also second round victory for fifth seed Richard Gasquet of France, who defeated Australian Bernard Tomic.