World champions Italy have been thrown into a state of alarm at the World Cup after doctors said on Tuesday that they do not know when goalkeeper Gianluigi Buffon will be able to return from a back problem. Buffon, part of Italy’s 2006 World Cup-winning team, was forced to come off at halftime of the Azzurri’s opening match against Group F rivals Paraguay, which ended 1-1.

He had been upbeat after Monday’s game, saying he expected to be fit within a few days, only for the optimism to be punctured by the medics. ”At the moment it’s not possible to give a date of return,” Dr. Enrico Castellacci said. ”This will be identified on the basis of objective clinical conditions”. Castellacci added that the problem regarded the sciatic nerve on the left side of the back of Buffon, who had an injury-hit campaign for Juventus last season.

The 32-year-old is still widely considered the best goalkeeper in the game and it would be a massive blow to the Azzurri’s hopes of retaining their title if he cannot recover shortly. Federico Marchetti took his place against Paraguay and is likely to stand in while Buffon is out. The 27-year-old worked his way into the Azzurri fold with consistently solid performances in Serie A for Cagliari over the last two seasons, but he only has a handful of caps and this lack of international experience risks being exposed in South Africa.

Napoli’s Morgan De Sanctis is the third keeper in the squad. Italy are already without playmaker Andrea Pirlo, a 2006 hero like Buffon, who will miss Sunday’s Group F clash with New Zealand after skipping the Paraguay game with a calf problem. Coach Marcello Lippi hopes to have Pirlo back for the last group game against Slovakia on June 24.