Shanghai Masters champion Novak Djokovic said he still has unfinished business this season after delivering the perfect response to being knocked off the men's top ranking.

The soon-to-be-married Serb ceded the world No 1 spot to Rafael Nadal, but his reaction has been emphatic with an unbeaten run in China adding two titles to his collection.

Immediately after Nadal returned to No 1 by reaching the China Open final, Djokovic proved he was not about to go away by defending his title from the Spaniard in straight sets.

He then swept all before him in Shanghai to retain a trophy for the second time in two weeks, outlasting Juan Martin del Potro in Sunday's thrilling final to win his 20th consecutive match in China.

Djokovic said he had not yet contemplated next year's Grand Slams and was still focused on 2013, with the Paris Masters, World Tour Finals and Davis Cup final still to come.

"Well, I'm still in this year. It hasn't finished," said the world No 2 after his win over del Potro. "I really will try to do my best till the end of the season, then I'm going to start thinking about what my goals are for next year."

Nadal has unquestionably been the stand-out player this season after making a phenomenal return from injury to claim 10 titles including the French and US Opens.

But Djokovic has been no slouch, retaining his Australian Open crown, narrowly losing to Nadal in the semifinals at Roland Garros and again in the final at Flushing Meadows. He was beaten by Andy Murray in the Wimbledon final.

Djokovic's chances of finishing ahead of Nadal as year-end No 1 are slim as the Spaniard, who was out injured this time last year, has no points to defend in the rolling rankings.

"I put myself in a better position right now with back-to-back wins," Djokovic said of his hopes of returning to the top spot.

"But the fact that if I would win, I would put myself in a better position, did not affect my motivation. My motivation is there always, especially when I'm playing finals of such a big event.

"I wanted this title as much as my opponent. That's what's going to stay forever."

The six-time Grand Slam winner has won five titles this year. He will now defend his title at the World Tour finals and attempt to win the Davis Cup for a second time in next month's decider against the Czech Republic.