Nakano was tipped to become a Honda test rider, but was thrown a potential MotoGP lifeline when Kawasaki began pushing for their former rider to steer a possible third ZX-RR, to be run by 125 and 250cc team manager Jorge Martinez 'Aspar' next season.

Unfortunately for Nakano, Aspar wanted a Spanish rider to please his sponsors and the whole project eventually broke down, ending Nakano's final hope of remaining on the premier-class grid.

A place as a test rider for any of the Japanese teams would have been possible, but at the age of 32 Nakano believes he has plenty of racing potential left and has chosen to take on the new challenge of the World Superbike Championship - where he will ride Aprilia's brand new RSV4 alongside Biaggi in 2009.

Biaggi and Nakano both have similar riding styles, inspired by their success in 250cc grand prix racing, as well as experience in leading development of a brand new motorcycle.

"I believe that Nakano can find with Aprilia the correct encouragement to reach for the top," stated Leo Francesco Mercanti, responsible for product and racing development at the Piaggio Group. "We have trust regarding his talent in this competition, and his experience in development of a motorbike."

Alex Hofmann, Roberto Rolfo and Alex Debon had also been linked to second the Aprilia WSBK seat.

Nakano's departure means that the only MotoGP riders on the 2009 grid to have raced a 500cc machine will be Valentino Rossi, Loris Capirossi, Sete Gibernau and John Hopkins.