The Azzurri missed the chance to take control of Group D as they went down to a Bryan Ruiz goal just before half-time in Recife on Friday.
The result eliminated England and sent Costa Rica through to the last 16, leaving Italy and Uruguay to fight it out for the other place in the top two.
Prandelli was quick to pay tribute to Costa Rica after the final whistle but admitted that Italy had been poor.
"We knew this would be a particularly tough group. We will try to recover all our energy for the Uruguay game," said Prandelli.
"We didn't get our tactics wrong. They were very, very aggressive and we were trying to find different ways into the game but we didn't manage it."
Prandelli added on Sky Italia: "It has been a bad loss.
“We have another game to play and clearly the approach must be different than this.
“I tried to change something, but also those who came on didn't make the difference. We have tried also to have a numerical superiority in the midfield, but we weren't quick.
“If we had scored one of the chances Mario Balotelli had, probably it would have been different.
“But we must think only about recovering.. We will give everything against Uruguay."
Antonio Cassano, who came on at half-time, agreed that Italy now had to concentrate on bouncing back quickly ahead of their meeting with Uruguay on Tuesday. A draw in Natal would be enough to send Prandelli's men through.
He said: “The most important thing is to recover energies. We will play a big game against Uruguay, and the loss hasn't been a physical problem.”
Goalkeeper Gianluigi Buffon applauded Costa Rica for holding on to seal a second straight victory and clinch a place in the next round.
He said: “We thought to do better, we thought to prepare in a good way for the match and we believed we would make it hard for them and win.
“Instead, we have had more difficulty and Costa Rica managed the match well after taking the lead.”