Lazio full-back Stephan Lichtsteiner has fractured the third metacarpal bone in his right hand.
The defender fell awkwardly during Tuesday's training session and was taken to hospital for x-rays when the swelling did not go down.
A statement from the Biancocelesti website confirmed a fracture of the third metacarpal bone in his right hand.
It is possible he'll be able to play on Saturday against Genoa with the aid of a protective cast, but more tests will be needed over the next few days to decide if he can make it.
Betting on Serie A? Bet365 are offering a 100% deposit bonus, up to £200 - find out more