Renault can replace Heidfeld during 2011

Nick Heidfeld's new contract with Renault allows the team to replace him with Robert Kubica at any point in 2011.

That is the claim of the specialist publication Speed Week, amid earlier suggestions a solid one-year term might have been the wiser choice for the Lotus-sponsored team before injured Pole Kubica makes a bid to return in 2012.

Heidfeld's lawyer Dr Stefan Seitz said he would not comment on contractual matters, but he did say: "This is a performance sport, with performance deciding who sits in the car at the end of the day."

With a statement provided by manager Daniele Morelli, Cologne newspaper Express quotes Kubica as saying: "With special methods I want to shorten the healing time and return this season.

"The accident will make me stronger, exactly as in the past," added Kubica, apparently referring to his horror crash in Canada in 2007 and his road crash of 2003.

On Friday, the 26-year-old moved out of the intensive care unit and into the Santa Corona hospital's rehabilitation unit.

Fernando Alonso, who is currently wearing a sticker on his helmet depicting his injured friend's helmet, told CNN last week that he feared initially that Kubica would not survive.

"Now it seems that he is improving, the operations from a medical point of view have been successful," the Ferrari driver told Spanish reporters during the Barcelona test.

"But we know that in F1 everything has to be perfect, so that is now the question about how he is going to go over the coming months.

"We also know that Robert is not normal, he has a lot of inner strength and I am sure he will recover better than people expect now," added Alonso.