Renault boss Patrick Faure has admitted that the French team made a mistake in bringing in Jacques Villeneuve to replace Jarno Trulli, who subsequently contested two races with Toyota.

Talking to Eurosport, Faure said: "I think we made a mistake and we must own up to it.

"I think we, both Flavio Briatore and myself, probably under-estimated the effects of a ten-month lay-off - even for a world champion with the experience and talent of Jacques," added the Frenchman. "To expect him to come straight in and score points immediately was probably unrealistic.

"F1 has moved on a year," he continued. "It is faster, the drivers have to cope with even more G-force; Jacques has found out and he's even in great shape! But the ten months he took off made it very, very difficult for him. It has unquestionably not been a success."

Following months of speculation, during which time there were numerous reports of the Canadian taking part in secret tests with WilliamsF1, the 1997 champion was involved in an amazing deal, which in the space of 24-hours saw him sign two F1 contracts - one to drive for Renault for the remainder of the 2004 season, the other to drive for Sauber in 2005.

"I don't think his problem has been re-adapting to Formula 1," admitted Faure. "I just think that, physically, he needs a few more months of competition to find top gear. He is the first to admit it when we have spoken.

"This signing has not been a success," he added. "Clearly we made a mistake."

It's thought that Villeneuve will drive the Sauber for the first time, next month at Barcelona.