Tennis: Keeping the No 1 spot is 'hard' - Djokovic

Novak Djokovic spoke Saturday of the challenge he faced maintaining his number one ranking, with Rafael Nadal set to unseat him from the top spot in Sunday's China Open final.

The Serb is on his 101st week as the top-ranked player, but Nadal will return to number one on Monday after he made it into the final in Beijing when his semi-final opponent Tomas Berdych retired injured.

Nadal's return to the top for the first time since July 2011 marks an astonishing comeback for the 13-time Grand Slam champion, who spent the second half of last year on the sidelines injured.

Djokovic said that being number one "is an ultimate goal and challenge for anybody".

"I know how hard it is because I've been fighting for that place for last couple of years and I know what a player needs to do in order to end up (the) year at number one," he said.

He also spoke of his desire to finish the season strongly.

"It's still not lost for me. He's going to be number one for Monday, but as I said the season is still not over," he said.

Djokovic has been in dominating form at the China Open, where he has an unbeaten run stretching back to 2009. He has won three of the four last tournaments, and did not attend in 2011 due to injury.

But Nadal has had the beating of Djokovic this season, coming out on top at the semi-finals at Roland Garros and last month's final at the US Open, as well as the Canada Masters.