Italy v Paraguay - Match highlights
Italy goalkeeper Gianluigi Buffon has been ruled out of Sunday's Group F match with New Zealand because of a herniated disc in his back.
The 32-year-old was injured during Monday's 1-1 draw against Paraguay and substituted at half-time.
There are fears that he may not play again during the World Cup.
Italy team doctor Enrico Castellacci said: "It's not easy to make a prognosis but it's a small margin and Buffon strongly wants to recuperate."
Buffon initially said he hoped "to recover in two days" but the Azzurri may now have to defend their status as world champions without him.
The world's most expensive goalkeeper - he cost Juventus £33m when they signed him in 2001 - missed training on Wednesday and tests on his injured back showed a small herniated disc as well as a sciatic problem.
"The hernia is small, but even a small hernia can cause great pain," added Castellacci.
"There is a desire on Buffon's behalf to recuperate, a chance that we have no right to take away."
Buffon was replaced by substitute Federico Marchetti against Paraguay and the Cagliari keeper looks likely to start against the All Whites in Nelspruit.
But defender Giorgio Chiellini, who also plays alongside Buffon for Juventus, admitted being without him would be a huge blow.
"A good goalkeeper is just as valuable as a striker who scores a lot of goals," stated Chiellini. "It's obvious how much he's worth to the team."
Buffon is regarded as the one of the best goalkeepers in world football
There was good news for Italy, however, about playmaker Andrea Pirlo's fitness, after he sat out their opening match with a calf problem.
"He has now been subjected to [an MRI scan], he is training and is running and things are going according to the schedule set out at the beginning," said Castellacci.
"The objective was for him to return in the third game or the last 16 and he should be ready for [one of] those."
Italy are looking for an improved performance against New Zealand, although coach Marcelo Lippi insisted they had made a satisfactory start to the tournament.
"Italy is right here. We're here tactically, physically, with our hearts, we're here full stop," he said.
"I just regret that we did not get the points we deserved (against Paraguay), but sometimes that's what happens, you get less than you deserve.
"The important thing is this was not a decisive game. What is important is that people now realise we are here and have got our act together."
De Rossi equalises for Italy