Madrid Masters tennis promoter Ion Tiriac on Friday promised a gradual improvement in traction on the new blue courts which have come under fire from players this week.

Rafael Nadal and Novak Djokovic have led the criticism of the slippery surface and Romanian billionaire Tiriac admits that player complaints are valid.

However, he said no one is complaining about the colour which gives a better image of the balls fot the worldwide television audiences.

“The court is slippery and I apologise,” said the former Davis Cup player, manager and impresario who has spent four decades in the game.

“We wanted to make sure that we had no player injuries, no ankle problems.

“As a result, the court experts rolled the base with too much pressure.

“When the blue sand was put on top it was unable to meld with the base, creating the slippage.”

But Tiriac said that after striking a maintenance deal with the city of Madrid, the blue courts will remain in place year-round at the Caja Magica and will eventually be as comfortable to play on as traditional red clay.

Tiriac said that the ATP must now deal with any players who have objections, deciding if they must compete or face sanctions in 2013.

“It’s a pity,” he said of Nadal’s threat, echoed by Djokovic. “I would be very sad if they did not play.

“The players are right when they say it is too slippery, We are working daily to fix that and things are getting better. There are still three days to go this week.”