Oct.24 (GMM) Alex Wurz has denied suggestions that his decision to vacate his Williams seat prior to the Brazilian grand prix may have not been entirely voluntary.

When Japanese test driver Kazuki Nakajima stepped in to replace the veteran Austrian, it was already rumoured that Toyota may have paid out Wurz to the tune of a six-digit figure.

Additionally, team co-owner Patrick Head is quoted as telling the Swiss magazine Motorsport Aktuell that deposing 33-year-old Wurz was one of the "tough decisions" that need to be made in a "tough business" like formula one.

Head added that Wurz was "invited" to vacate his car for rookie Nakajima, who is strongly backed by Williams' semi-works engine partner Toyota.

"The fact that for large sections of the year we only won points with one car was discussed internally," the Grove based team's engineering chief and long time partner of Sir Frank Williams said.

Williams' technical director Sam Michael also suggested that Wurz's early retirement was not entirely voluntary.

"We obviously wanted to defend our (fourth) position in the championship. So we had to reorient out focus," the Australian hinted.

Wurz denied that he was asked to step down.

"That is simply not true," he is quoted as saying. "I was simply no longer prepared to give 100 per cent of myself in the car."

Wurz's teammate in 2007, Nico Rosberg, said he missed Wurz's vast technical experience at Interlagos when it came to setting up the FW29 car.

"It was a difficult situation (with Nakajima)," the young German admitted.

"Alex would definitely have been a help."