Giampaolo Pazzini sprained his left ankle against CSKA Moscow and is a major doubt to face Napoli, confirmed the Inter website.
The striker limped off a few minutes into the second half of Tuesday's 3-2 Champions League victory.
He had suffered the injury before the break when he landed awkwardly, perhaps in part due to the synthetic pitch in Moscow.
“Pazzini underwent tests performed by Professor Franco Combi and was diagnosed with a sprained left ankle,” read a statement.
It is not clear how bad the sprain is or when he will be able to recover, but Pazzini becomes a major doubt to feature in Saturday's Serie A clash against Napoli.
Meanwhile, Douglas Maicon, Andrea Poli and Dejan Stankovic took part in a full training session today.
Ivan Cordoba, Thiago Motta, Andrea Ranocchia and Wesley Sneijder had individual training schedules to help recover fully from their injuries.