US golf legend Jack Nicklaus is the inspiration behind world number one tennis ace Rafael Nadal's trademark powerful serve, the tennis player's coach and uncle said on Sunday.

"I saw a video by Jack Nicklaus that changed my vision. In it Nicklaus said: 'First strike far, then we will think about getting the ball inside," Toni Nadal said in an interview published in daily newspaper ABC.
"I said to myself: 'This man must be right'." That is what I applied with Rafael. First strike hard, then we will get the ball inside," he added.  Toni Nadal, 49, who has been Rafael's coach since the player was four, said hard work was behind his nephew's success.  "You either have talent or you don't. But what makes the difference is hard work," he said.  "Since he was a child I set a long-term goal for him: to be a great professional. In life you have to have hope to advance."

Earlier this month Rafael became the seventh man in history -- and the youngest at 24 -- to achieve a career Grand Slam as he earned his first US Open title.  The ATP has said he is set to finish as the world's number one this year for the second time in three years.