The Italy coach has told the Fiorentina striker that he will not rule him out of his World Cup plans until the last possible moment as he recovers from injury.
Rossi strained ligaments in his right knee during Fiorentina's win over Livorno earlier this month and has been sent to America for tests.
The 26-year-old is top scorer in Serie A this season with 14 goals, and Prandelli insisted he will give the striker as much time as possible to be ready for Brazil
"Rossi should stay calm," he told La Gazzetta Dello Sport. "Considering that I know him, and I will wait until the last (moment to decide)."
Prandelli also refused to rule out selecting Sassuolo striker Domenico Berardi for his squad but admitted it may be too soon for the 19-year-old, who has scored 11 goals this season.
"It's about proving quality," he added. "Let's let him grow up, and not give them too much responsibility."