Michele Pirro will debut a prototype version of next year's 2017 Desmosedici during a private test at Valencia this week.

The outing explains why factory test rider Pirro is not flying out to replace the injured Andrea Iannone in this weekend's Japanese MotoGP.

However, Pirro is ready to once again step-in should Iannone not be fit for the following Phillip Island round.

"It would be nice, personally I feel ready," Pirro told GPone.com. "Of course I'm sorry for Iannone, I understand very well what he is facing, I too have had to deal with the same [injury]. Unfortunately, the vertebrae is never like a broken wrist."

If Iannone does not ride at Phillip Island, it would stoke speculation that retired former champion Casey Stoner might return for his home round.

However it seems unlikely that the Australian, unbeaten at Phillip Island from 2007-2012, would step-in at such short notice given the physical preparation needed for a MotoGP race distance. Stoner last rode a MotoGP bike during the Austria test, in July.

Ducati has always left the door open to its star test rider making a one-off racing return, either a as wild-card or replacement, but Stoner has so far politely declined each opportunity. As appears to have been the case for Motegi.

Jorge Lorenzo will make his Ducati debut at the Valencia post-race test in just over a month. However, it appears Yamaha are not keen to release the triple world champion for a further Ducati test at the end of November.