Rafael Nadal has denied he has ever used a banned substance to get an edge or to speed up recovery from injury.

Asked for his reaction to Maria Sharapova's failed drug test, the 14-time Grand Slam champion took the opportunity to address speculation he has used performance-enhancing drugs.

The Spaniard, 29, said he was "a little bit tired" of the rumours, adding: "I am a completely clean guy.

"I have never had the temptation of doing something wrong."

Nadal added: "I believe in the sport and the values of the sport.

"The sport is an example for society. It is an example for the kids and if I am doing something that goes against that, I will be lying to myself, not lying to my opponents."

Nadal has never failed a drugs test but has been the subject of speculation that he dopes.

In 2011, former French Open champion Yannick Noah wrote a newspaper article saying Spanish sporting success was due to doping.

A year later, a French TV show featured a life-size likeness of Nadal filling up his car's gas tank from his own bladder before being pulled over by traffic police for speeding.

Then in 2013, Belgian former professional player Christophe Rochus questioned Nadal being able to dominate the 2012 French Open and then be injured two weeks later at Wimbledon.

Nadal said he has taken advantage of some new treatments for his knee problems, like stem-cell therapy and Platelet Rich Plasma (PRP) therapy, often known as blood spinning.