Italian goalkeeper Gianluigi Buffon could be ruled out of the rest of the World Cup with a back injury, according to reports.

Buffon was forced off the field at half-time during Italy's 1-1 draw with Paraguay with what was later diagnosed as a sciatic nerve problem.

Italian football federation vice president Demetrio Albertini said that "we are confident that our goalkeeper will make a speedy recovery."

However, doctors are struggling to diagnose the problem and Italy's chief medic Enrico Castellacci said the problem is "serious", adding: "At the moment, it's impossible to estimate when he might return."

Reports suggested that Buffon may be out for 10 days, but it appears that his tournament may be over. Italy may give Buffon a cortisone injection, but he will require surgery on the disc that is pressing on the nerve.

Buffon said on Wednesday that "I am very worried about my World Cup."

Palermo goalkeeper Salvatore Sirigu is in line to replace Buffon if Italy decides not to risk the Juventus keeper.