Mattia Pasini will test for the Pramac Ducati team on Monday's official MotoGP test day at Brno following this weekend's Czech GP.
The Italian, who goes into the weekend fifth in the 250cc standings on an Aprilia, has been called up to take the place of the team's regular rider Mika Kallio, who has been drafted into the works Ducati team in place of Stoner.
Superbike rider Michel Fabrizio has filled Kallio's seat at Pramac for the race weekend, but team boss Paolo Campinoti has elected to offer Monday's test to Pasini.
"This idea has come together with Ducati after as Mika's bike would have remained without a rider after he joined the [works] Ducati team for the next three races," he said.
"Mattia has demonstrated during this season that he deserves this opportunity and for these reasons we're happy and proud to have him with us, even if for only one day."
Pasini added: "I want to thank Ducati, Pramac Racing and team principal Paolo Campinoti, who are giving me this magnificent opportunity to try their bike at Brno on Monday.
"It will be an important test for me as I will have the possibility to understand if I will be able to ride a MotoGP bike. I have always liked difficult challenges and I am ready for this one."