Manchester City striker Mario Balotelli has suffered a recurrence of his right-knee problem during a practice match at the Italy training camp.
The 20-year-old had to be helped off the pitch after feeling discomfort in a match against Italy's under-18s.
He is set to miss Friday's Euro 2012 qualifier with Estonia and Tuesday's friendly with the Republic of Ireland.
"I'm worried and will get in contact with the medical staff at City," said Italy team doctor Enrico Castellacci.
Balotelli, who joined City from Inter Milan for £24m in the summer of 2010, had surgery on his right knee last September after being injured in a Europa League match and suffered a similar injury in January.
The striker scored 10 goals in his first season at Eastlands.
Castellacci, the doctor who assessed him in Italy, said that Balotelli "would not recover in time" for Friday's game against Estonia and to play against Ireland would be "an unnecessary risk".