Rafael Nadal admits his return to top the world tennis rankings after a serious knee injury is the greatest achievement of his illustrious career.
Nadal, in London for the season-ending ATP World Tour Finals, is set to cap a remarkable recovery by finishing the year at No.1.
The 13-time grand slam champion was sidelined with potentially career-threatening knee tendinitis for seven months until early this year.
The 27-year-old, who has struggled with knee problems for much of his career, returned to win the French and US opens, and five Masters events before reclaiming the No.1 spot last month.
“It is the most difficult thing I did in my career. I’m 100 per cent sure of that.
“After seven months of not even being able to practise tennis, I came back and won from the beginning and was very soon able to have success in the best tournaments and against the best players.
“Sure, I had doubts if I would come back like this. The doubts I had were normal.
“I have doubts before every match and much more when I am injured for seven months.
“I didn’t know how the injury was going to improve or if I could get back on tour.”
Nadal needs to win two of three group matches against opening opponent David Ferrer, Tomas Berdych and Stanislas Wawrinka to guarantee top spot ahead of No.2 Novak Djokovic.
But he is adamant that regaining his No.1 crown means less than the emotions he felt in his two grand slam triumphs this year.
“I already finished two years at No.1 in the rankings so, if that happens again, great.
“But if not, I don’t think it is going to affect my standing in the history of tennis.
“It was a goal for me in 2008 because then I felt I had a great career and I would be sad if I played that good and never got No.1.
“Today the goal is to be healthy and competitive.”
Nadal has never won the Tour Finals, losing his only final to Roger Federer in 2010.
The Spaniard has called on ATP chiefs to be fairer to star players by providing a different surface each year for their flagship World Tour Finals.
Nadal is unhappy the prestigious event has been staged indoors on hardcourts for the past nine years, with Shanghai and London’s O2 Arena being the venues since 2009.
He believes it is unfair to players who don’t thrive indoors but have already proved their class by qualifying for the eight-man competition by succeeding on a variety of surfaces throughout the year.
Nadal is suggesting the tournament be played outdoors on a different surface each year, giving clay, grass and hardcourt specialists at least one good chance to win every few years.
“I know it won’t happen in my generation. It’s not for me. I say it for the next generation …” Nadal said.