Gianluigi Buffon left at halftime of Italy's 1-1 draw with Paraguay. ((Francesco Monteforte/AFP/Getty Images) )

Italy goalkeeper Gianluigi Buffon has been diagnosed with a herniated disk, putting his World Cup at risk.

Team physician Enrico Castellacci said Wednesday that the recovery period would "not be brief," adding that it was impossible to set a specific return date.

"We'll do everything we can to get him back but don't ask me for a prognosis of when," Castellacci said.

Buffon exited after the first half of Italy's 1-1 draw with Paraguay on Monday and was replaced by backup Federico Marchetti. He underwent an MRI at a hospital in Pretoria on Wednesday.

The defending champions next face New Zealand on Sunday, then round out Group F play against Slovakia four days later.

"Clearly he can't play Sunday," Castellacci said. "It's a very small hernia, but even small hernias can create a lot of pain."

Buffon has been bothered by back problems with his Juventus club recently, and Castellacci said the injury wasn't new.

"He needs to rest now. He shouldn't do much physical movement," Castellacci said. "For now, we're resorting to therapeutic treatment. If the therapy doesn't heal the injury, then Juventus would have to decide on an eventual solution together with [Buffon]. Surgery is often not required for minor herniated disks."

Castellacci said Italy had already obtained consent from FIFA to administer pain medication to Buffon.

Meanwhile, coach Marcello Lippi and the rest of the squad were preparing to play without Buffon. Defender Giorgio Chiellini, a teammate of Buffon with both Italy and Juventus, already knows what that's like.

When Buffon missed several periods at his club this past season due to knee, thigh and back problems, Juventus struggled, too.

"A good goalkeeper is just as valuable as a striker who scores a lot of goals," Chiellini said. "It's obvious how much he's worth to the team."

When Italy won the 2006 World Cup, Buffon was beaten only once in open play over seven matches — and that was an own goal by Cristian Zaccardo against the United States. He also conceded a goal to Paraguay following a free kick — but wasn't to blame — in Italy's opener at this tournament.

Marchetti was never really tested in the second half against Paraguay, but will now face more scrutiny. He's had two solid seasons with small Serie A club Cagliari, but was playing in Serie B with Albinoleffe as recently as 2008.

Somewhat similarly to Marchetti, Chiellini was rushed into the starting team at the 2008 European Championship when captain Fabio Cannavaro injured his ankle during Italy's opening training session in Austria.

Despite that experience, Chiellini was leaving it up to Buffon to offer psychological encouragement for Marchetti.

"Goalkeepers live in their own world, so I think the best person to help him out is Gigi. The only thing I can provide is tranquillity. He doesn't need my advice," Chiellini said. "He's got a lot of quality and he won't have any problem replacing Gigi."

Napoli's Morgan De Sanctis is now Marchetti's backup.

On a more positive note, Castellacci said that midfielder Andrea Pirlo, who also had an MRI on Wednesday, is nearly ready to return after having injured his left calf.

"The objective was for him to recover for the third game and we're on track," Castellacci said.