The fight between Roger Federer and Rafael Nadal to be world No 1 at the end of the year could go all the way and only be settled at the ATP World Tour Finals in London.

While Federer may not have imagined finishing the season as World No 1, he has said that the World Tour Finals are his main target and he now has a realistic chance of overtaking Nadal to reclaim the top spot.

Nadal has said that he will be missing the Swiss Indoors in Basel, taking place this week, due to a knee injury.

Earlier in the month Federer was incredible in his 6-4 6-3 victory over Nadal in the final of the Shanghai Masters. It was Federer’s sixth trophy of the season and underlined a change in fortunes against his long-time rival.

Federer is now just 1,960 points behind Nadal. There are 500 up for grabs in Basel and a further 1,000 available at the indoor tournament in Bercy in Paris.

As a result, the battle for the year-end top spot could go all the way to the ATP finals, taking place from November 12 – 19 in London, and the winner there is set to receive up to 1,500 points.

Both players have won six titles this year, splitting the four Grand Slams between them. However, Federer looks to be pulling ahead. He ended a series of five straight defeats to Nadal in Basel last year before beating him in the Australian Open final in January. He has now won their last five encounters, including all four this year.

Federer is the top seed in Switzerland but he will face competition in the form of Marin Cilic, David Goffin and Juan Martin del Potro.