Rafael Nadal `happy to keep going` after disastrous year

Nadal says he is happy with the motivation that keeps him going.

Tennis superstar Rafael Nadal said Tuesday he was "more than happy" to keep playing on after his worst season in a decade.

The former world number one ended his reign as French Open king at the quarterfinal stage this year and also failed to reach the semifinal of the US Open, Australian Open and Wimbledon.

This has led to growing speculation that the 29-year-old Spaniard, one of the most exciting and tenacious competitors of his generation, was past his best.

"Today I am more than happy to keep going. I start another year in one month and I`m very excited about it and I have the motivation to keep going," he told reporters in Manila.

He said he had "no idea" how long he will be able to compete at the sport`s top level.

"For me it doesn`t matter if it`s one, two, three, four, five, six years. I really don`t think about it. I go day by day," he said.

After embarrassingly early exits from Wimbledon and Flushing Meadows and dropping to number 10, Nadal rallied in the latter part of the year to end 2015 as the world`s fifth-ranked player.

He said he was "happy" with his form in the last three months of the season.

Earlier on Monday he said he was hopeful of carrying this form over to the Australian Open, which starts on January 18 next year. 

His last two seasons were plagued with injuries and last year he had surgery to remove his appendix.

Nadal is in the Philippine capital this week to play in a parallel International Premier Tennis League (IPTL) tour, which promotes a shortened, speeded-up version of the game that organisers said is more television-friendly than the traditional format.

The IPTL tour began in Japan last week and will also have stops in India, Dubai and Singapore later this month.