World number two Rafael Nadal [Images] has a serious problem with his foot which is likely to affect the rest of his career, his uncle and coach Toni Nadal has said.

"He's been affected by an injury to his foot since 2005. He has to learn how to live with it and so far he has managed for two years," Toni Nadal said in an interview with the Spanish daily Diario de Mallorca on Wednesday.

When asked how serious it was, he responded: "I prefer not to answer. It's very serious. I don't know (if it's career-threatening). I'll let the doctor reply to that. He has to take a lot of precautions when he plays."

Much of Rafael Nadal's game is built on his athletic ability and pace around the court but Toni Nadal said he had worked to modify his game rather than reduce the number of matches he played.

"We are pleased with the season just finished, with the injury and everything. His play has improved and the matches have been less intense," he said.

"Roger Federer [Images] is a fully-rounded player; Rafael has a different style. The key factor has been to shorten the length of matches and we have achieved that.

"His problem is that he has to play to maintain his physical tone and fitness levels. There's no other way to do it than by competing."

The 21-year-old won six major tournaments in 2007 including his third French Open title at Roland Garros.

• Complete tennis coverage
• All you want to know about Sania Mirza