The veteran striker suffered a potentially career-threatening torn anterior cruciate ligament during his side's 2-0 win over Cluj
The Argentine striker, who helped propel the Nerazzurri to Champions League victory in 2010, fell awkwardly after getting his studs trapped just seven minutes into Thursday night's Europa League clash.
Stramaccioni is distraught that his forward, who was stretchered off at San Siro in tears, looks set to miss the remainder of the campaign, with reports circulating that his career is at risk.
"Unfortunately, this injury rather ruined the night," Stramaccioni told reporters after the match.
"It is a lesion to the anterior cruciate ligament, damage to the collateral ligament and capsule. It is a terrible injury and totally new compared to the problems he had in the past.
"There’s a one per cent chance of this happening, but it happened to Diego. We now just need to know when he’ll have the operation.
"It’s awful news, as we all care for him as a person as well as a player. I am personally very close to him and feel so sad right now."
Inter's city-rivals AC Milan have also pledged a message of support to the player, wishing him the quickest possible recovery.
All of Milan are profoundly saddened by the injury sustained," a note on the club's official website read.
"We are close to the great champion Diego Milito, an extraordinary opponent of many encounters. We hope to see him back on the pitch again soon."