The 28-year old midfielder underwent a scan on his hamstring and the end result was that he will likely be out of action until the Boxing Day fixture with Motherwell.
Flood sustained the problem during the 3-1 loss to Heart of Midlothian at Pittodrie and has been undergoing rehab on the affected area.
A statement on RedWeb said: “Scans have confirmed that midfielder Willo Flood has suffered a small tear to his hamstring and will be out for between 4-6 weeks.”