Italy midfielder Riccardo Montolivo will miss the World Cup after breaking his left leg during the 0-0 draw with Republic of Ireland at Craven Cottage.
The AC Milan player, 29, was carried off on a stretcher after a challenge from Reading defender Alex Pearce.
Italy team doctor Enrico Castellacci said: "I haven't seen the X-ray yet to evaluate the extent of it, but for a broken bone you can expect surgery."
Italy face England, Uruguay and Costa Rica in World Cup Group D.
Montolivo, winning his 58th cap, lasted just eight minutes of Italy's penultimate warm-up game, and was immediately taken to a London hospital for X-rays, which confirmed the damage.
He was replaced by former Liverpool midfielder Alberto Aquilani, who went off at half-time complaining of dizziness.
Aquilani's Fiorentina team-mate Giuseppe Rossi may have secured his place in Italy's 23-man squad for Brazil, though, by playing for 70 minutes on his return from knee trouble.