SHANGHAI (REUTERS) - Novak Djokovic breezed into the third round of the Shanghai Masters with a 6-2 6-1 victory over Martin Klizan on Wednesday, but Ivo Karlovic made sure Rafa Nadal had to work a lot harder.

Nadal eventually won through 7-5 6-7(4) 7-6(4) after two hours and 43 minutes of a closely-fought encounter.

After trailing 3-5 in the opening set, Nadal produced a series of stunning returns to break Karlovic in the 10th game to claim the lead.

The Croat, however, refused to give up, prevailing in the second set tie-break to force the decider, which again went to the wire before the Spaniard claimed victory.

There was no such drama for Djokovic as the world No. 1 dropped only three games against Klizan.

Eyeing a third Beijing-Shanghai double, Djokovic converted half of the 10 break points that came his way to sweep aside his error-prone Slovak opponent.

"Klizan is a very flashy player," Djokovic, who won last week's China Open in Beijing, said.

"He can play very fast but with a tendency to make a lot of unforced errors, which he did. He made my life a bit easier on the court today.

"I was trying to serve, move him around the court. Just played as much as I needed. It was enough to win," the Serbian said after improving to a 13-match winning streak.

French Open champion Stan Wawrinka also maintained his winning run with a 7-6(3) 6-3 victory over Viktor Troicki to set up a third-round contest with Marin Cilic.

Third seed Andy Murray beat American Steve Johnson 6-2 6-4, Bernard Tomic eliminated seventh seed David Ferrer 6-4 6-2 and Japan's Kei Nishikori overcame Australian Nick Kyrgios 1-6 6-4 6-4.