To progress to the last eight, the Azzurri need to win and hope Spain or Croatia are victorious or draw 0-0 in their match. A scoring draw in the Spain game would complicate the mathematics of a three-way head to head.
"There will be three or four changes," Prandelli told a news conference on Friday, the day after Italy let the lead slip in a 1-1 draw with Croatia.
"Obviously in the third game, with regards to who I pick, we need freshness. We have no margin for error."
"I shouted at him for 15 minutes to play deeper," he said. "For me his potential is huge, but he has to do more. We are not a team that plays on the counter-attack. He had to be told the truth."
"Diamanti has the class to play as a second striker if the team is playing high up the park," added Prandelli who thought his side sat back too much to protect their 1-0 lead against Croatia and should have attacked more in the second half.
"Spain will go on the field to win like they have always done in recent years," he said.
"After all their great football, the great spectacle, the fact everyone wants to copy their team, we think they'd think about conspiracies? Impossible."
