Rafael Nadal doubts if he could still win another Grand Slam title under the helms of his uncle and coach Toni.

Nadal remains loyal to Toni but the “King of Clay” is not sure whether he will still add another major title in his illustrious tennis career.

"I don't know when that's going to happen and I don't know if that's going to happen," Nadal said, reports Reuters UK.

Nadal also admitted that despite his 2015 setbacks, this year has been the possible season for him. However, he believes the last three months of the ATP World Tour season had become “much better” for the Spaniard.

For the first time in his 11-year career, Nadal has not won a major title in a season and struggling mightily in the first half of this year. But Nadal has shown a glimpse of his old form after reaching the final round of the China Open and the Swiss Indoors, where he was defeated by Novak Djokovic and Roger Federer. The Spaniard also defeated Andy Murray and Stan Wawrinka, both in the top five of ATP World rankings, during the World Tour finals in London.

According to Nadal, he feels he is getting back to the level of play that won him 14 Grand Slams. “I have already had a long career and it could be difficult to point at one or two challenges – to overcome injuries has been one of my biggest challenges but never comparable to ones on court,” Nadal said, reports India Times. “You need to be fit to play – but once that happens, the challenges on court are particularly special.”

Nadal, who will open his season next year in Doha, is currently playing in Asia’s International Premier League along with the world’s best tennis players. He leads the Indian Aces and currently competes at the fourth-leg of the tournament in New Delhi.

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