The Serbo-Montenegrin hit-man picked up a serious knee ligament injury playing for the Kuip club's reserves on Monday evening.
Tests have revealed he has torn a ligament in his left knee and the Rotterdam club expect him to be sidelined for around 12 weeks.
"This is very annoying for him," sad Kuip coach Bert van Marwijk.
Lazovic joins fellow knee injury victims Gerard de Nooijer and Leonardo in the Feyenoord treatment room.
De Nooijer had surgery on Friday and is expected to be out until well into next year, while Leonardo is waiting to find out if his problem requires an operation.
