World No 1 Novak Djokovic lashed out at Madrid Open organisers and the ATP over the event's controversial blue clay courts after fighting off Spanish qualifier Daniel Gimeno-Traver 6-2 2-6 6-3 in the second round on Tuesday.

The defending champion, back in action after a two-week break following the death of his grandfather, said it was "impossible to move" on the Manolo Santana show court and accused tennis officials of ignoring players' concerns.

"I hit five balls throughout the whole match," the visibly irritated Serb, who had a bye into the second round of the Masters event in the Spanish capital, told a news conference.

"Everything else I was just trying to put the ball in the court so I just rely on my serve and getting some points eventually from his unforced errors," he added.

"For me that's not tennis. Either I come up with the football shoes or I invite Chuck Norris to advise me on how I should play on this court."

A host of players, including claycourt king Rafa Nadal and Roger Federer, have expressed concern about the decision to switch from traditional red clay to blue, which organisers say makes it easier for TV viewers to follow the yellow balls.

An ATP spokesman reiterated the governing body's position that the blue clay had been approved for one year and all feedback from the players would be taken into consideration when deciding on its future use.

Djokovic echoed comments from fellow professionals about the courts being slippery and called for a "serious discussion" once the tournament is over.

"I know for certain that there are so many players that I talked to these last three or four days that share the same opinion," he said.

"I take things very seriously regarding the surfaces and regarding our circuit.

"I think all the players' opinions have to be heard and have to be considered. This tournament and this decision to change to the blue clay is an example of players not being considered and heard and their opinions being ignored so I really hope that this is going to change in the future.

"I haven't heard a single player, not man or woman, saying they like blue clay."

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Djokovic's victory against Gimeno-Traver set up a clash against Swiss Stanislas Wawrinka or Austrian Jurgen Melzer.

He was joined in the last 16 by Czech sixth seed Tomas Berdych, who dispatched Kevin Anderson of South Africa 6-3 6-4 and will play French 12th seed Gael Monfils or Russian qualifier Igor Andreev for a place in the quarter-finals.

Fast-rising Canadian Milos Raonic set up a meeting with world No 3 Federer thanks to his 6-4 6-4 success against former No 3 David Nalbandian.

Raonic took a set off the Swiss maestro at the Indian Wells Masters in March and told a news conference he was planning to treat the 16-times grand slam singles winner as just another player on Wednesday.

"He's achieved a lot of great things but tomorrow when we step on the court he's just an opponent and somebody who wants the same thing I do," Raonic said.

"You respect him but not too much," he added. "He's just another player who's trying to take away from you what you want."

Nadal, the world No 2 who lost to Djokovic in last year's final, starts his campaign on Wednesday against Russia's Nikolay Davydenko.

- Reuters