LONDON (AFP) - Rafael Nadal is facing a race against time to be ready for the ATP Finals as he battles Novak Djokovic for the year-end number one ranking, admitting he is struggling with his serve.
The 33-year-old said he was happy to be in London after being forced to pull out of last week's Paris Masters at the semi-final stage with an abdominal strain, but admitted he was not serving at full tilt ahead of his opening match against defending champion Alexander Zverev.
Nadal is bidding to clinch the year-end number one spot in the ATP rankings for a fifth time -- he is currently 640 points ahead of Djokovic ahead of the season-ending tournament in London, starting on Sunday.
The Spaniard, who has never won the ATP Finals despite his trophy-laden career, dethroned Djokovic from the top of the rankings this week.
He has often struggled with injuries towards the end of the season -- missing the ATP Finals last year through injury and pulling out after just one match in 2017.
The top seed said he had only started practising his serving on Thursday and it had been "very slow".
Nadal, who won the French Open and US Open this year, said he had been happy with
Nadal's opponents in the Andre Agassi group are Daniil Medvedev, Stefanos Tsitsipas and Zverev.
The Bjorn Bjorg group features Djokovic, Roger Federer, Dominic Thiem and Matteo Berrettini.