The Italian rugby federation have announced that World Cup captain Sergio Parisse will not join up with the team in Rome on September 12 following surgery to drain a haematoma.
The 31-year-old Argentine-born No 8 has 112 caps for Italy and is their star player.
He underwent surgery in Paris on Tuesday to drain a haematoma - a swelling of clotted blood - in a muscle in his left leg, after he picked up a knock in Italy's World Cup warm-up Test defeat to Wales in Cardiff last weekend.
The federation said that Parisse was currently undergoing treatment with his Paris-based club Stade Francais and would meet up with the Italy "at a later date" in England.
"The goal is to optimise as much as possible the recovery process and to avoid any movements that are not strictly necessary," it said.
"Further updates on the player's condition will be issued after the national team has gathered."
Italy open their World Cup campaign on September 19 in Twickenham against France.