Nadal calls 'recovery from injury to reclaim No.1 ranking' his greatest feat

Spanish tennis player Rafael Nadal has admitted that it is the greatest achievement of his illustrious career to be able to battle a serious knee injury and return to the top of the world rankings.

According to Sport24, Nadal has arrived in London for the season-ending ATP World Tour Finals on the verge of capping a remarkable recovery by finishing the year at number one in the world.

That would be an incredible effort given the 13-time Grand Slam champion was sidelined with potentially career-threatening knee tendinitis for seven months from mid-2012 until early this year, the report said.

The 27-year-old Spaniard, who has struggled with knee problems for much of his career, returned to win the French Open and then the US Open, as well as Masters events in Indian Wells, Madrid, Rome, Montreal and Cincinnati before reclaiming number one spot last month, the report added.

Nadal said that it was the most difficult thing that he did in his career, adding that he was 100 percent sure of that.

He added that after seven months of not even being able to practice tennis, he came back and won from the beginning and was very soon able to have success in the best tournaments and against the best players.