The club have suffered another blow to their already depleted strike-force following the news of the 30-year's hamstring injury which is likely to keep him out for a month
The Italy international was substituted 30 minutes into the match and is expected to be sidelined for 30-40 days after the club revealed the extent of the injury.
An Inter statement read: "We have tested Antonio Cassano following the accident which occured during the first half of Inter-Atalanta, and results of his scan showed a second degree lesion myotendinous to his right hamstring."
The news comes less than a week after striker Rodrigo Palacio was ruled out for the same duration and, with Diego Milito also in the treatment room, it leaves Inter coach Andrea Stramaccioni with Tomasso Rocchi as the only available centre-forward for the visit of Roma in the Coppa Italia next Wednesday.
Rocchi netted his 100th goal in Serie A - his first in over a year - in Sunday's defeat, but speaking to the club's official website, the 35-year-old expressed regret that he could not celebrate reaching the milestone with a victory.
"I hadn’t scored for a long time and I needed to regain the right mindset to face matches and get my form back. But I can’t be entirely happy. It would have been better to celebrate my 100th goal with a win," he said.