Factory test rider Pirro is having three race outings this season as part of his deal, starting in Spain.
After two winless seasons and under a restructured management team following its acquisition by Audi, Ducati is using 2013 as a year of rebuilding and is not expecting instant success.
But having lagged behind the other prototype runners early in winter testing, it showed more encouraging form in the opening two races, with Andrea Dovizioso qualifying in the top six for both and finishing seventh twice.
Team boss Vito Guareschi said Jerez would be a big opportunity to make progress, especially with a third bike for Pirro.
"His GP13 will have some new development parts that will help us to focus on the development for the rest of the championship," Guareschi said.
"It'll be an important opportunity for us to learn more because the track is very different from the other two that we've raced on so far."
Pirro contested the 2012 MotoGP season on Gresini's CRT bike.
He was third among the CRT runners in the championship and took the best overall finish for a CRT bike when he took fifth in the Valencia season finale.