As reported by

Martin Caceres is to undergo surgery after fracturing the malleolus bone in his left ankle during this afternoon’s training session.
The defender will be operated on tomorrow, with a prognosis on his recovery time to be established afterwards.
The operation will be carried out by Dr. Flavio Quaglia at Turin’s Fornaca Clinic.

The official site does not talk about recovery time, but in injury cases similar the times are quite long by 60 to 90 days, Caceres risks seeing finished his season.