Italy defender Christian Panucci is waiting on test results after suffering an injury to his right knee early in training today.
The 35-year-old Roma right-back received treatment on the sidelines from Azzurri doctors before walking gingerly back to the dressing room.
"During training Panucci felt pain in his right knee and stopped training as a precaution," read an Italian Football Federation statement.
Panucci, who scored the goal against Scotland in November that secured the World champions a place at Euro 2008, was a contender to start Italy's opening fixture against the Netherlands in Berne on Monday.
Fellow defender Fabio Cannavaro was ruled out of the tournament on Monday after tearing ankle ligaments during the team's first training session in Austria.
At this point, coach Roberto Donadoni appears set to start Marco Materazzi and Andrea Barzagli in central defence. If Panucci is also unavailable, Gianluca Zambrotta will likely shift over to right back and Fabio Grosso will start on the left flank.
"Italy loses a lot without Cannavaro, but we've got the same desire we had at the World Cup," midfield maestro Andrea Pirlo said earlier today.
"Plus, there's extra motivation because Italy hasn't won a European Championship in 40 years. It's time to bring this trophy home. I came here to win."