Nadal enraged by Centre Court warning

World number one Rafael Nadal strongly denied that he was being coached on Centre Court at Wimbledon on Saturday and said he would take the accusation up with the tournament supervisor.

After battling through a five-set third round marathon against German Philipp Petzschner, the 2008 champion admitted he was "a little bit scared" about his knees but rejected claims that calling for a medical timeout had been gamesmanship.

Nadal was furious when umpire Cedric Mourier issued the warning to Nadal for coaching by his uncle and coach Toni. The Spaniard was really fired up, wagging his finger in rage.

"I was saying, we gonna talk with the supervisor later," he said.

"Toni wasn't giving me any tips. He was only supporting me," he added.

Asked afterwards if it was fair to be warned, Nadal said "Sometimes yes. Not today in my opinion. But yes, sometimes in the past, Toni maybe talks too much."

Nadal had to miss defending his Wimbledon title last year because of knee injuries. But this season he has swept all before him on the clay court circuit, landing the French Open for the fifth time.

His knee problems appeared to have resurfaced against Petzschner, Nadal calling the trainer several times and receiving treatment.

"I am a little bit scared about the knee," he said.

"I have a little bit of a problem on the right knee. But, you know, I have one day and a half to recover," he said. 

His next opponent will be unseeded Frenchman Paul-Henri Mathieu.

Nadal has already had treatment on his left knee. Treatment on his right knee awaits.

"With the new treatment, the left knee works perfect. So hopefully when I have the same treatment to the right (knee), hopefully that is going to be the same," he added.

Petzschner said he thought Nadal's timeout was "pretty clever."

"I don't know. Maybe he had something, maybe it was just a clever part to take a timeout there," the German said.

That provoked a frosty but firm response from Nadal.

"I have never called the physio when I don't have a problem, not at any time in my career," he said.

"If I call the physio today it was because it was the knee that was bothering me," he added.