The Colombian was magnificent at the back for his side on Saturday night but he was unable to celebrate the result as he was carried off with what looked like a nasty injury.
Inter have been monitoring the player's condition over the last 48 hours and they have now confirmed the worst as the stopper will need surgery.
A statement on the club's official website reads:
“Nelson Rivas underwent further examination on his injury this afternoon, and after a consultation, Professor Franco Combi and Professor Franco Benazza have decided that surgery is necessary for the reconstruction of the player's lateral ligament in his right knee.
“After the operation, which will be carried out over the next few days, the Colombian defender will undergo complete rest for around a week and then he will begin his rehabilitation.”
It's not the news Inter or Jose Mourinho wanted as they already have a number of injury problems at the back.
Midfielders Javier Zanetti and Esteban Cambiasso have already been covering in defence as the problems worsen for the 'Special One'.