Russell suffered the injury during the closing stages of the Rams' 3-1 home win over Leeds on Saturday after being on the receiving end of a heavy challenge.
The 23-year-old, who joined the club from Dundee United in the summer, underwent a series of scans on Monday which confirmed that he had a fracture to his fibula similar to the one he sustained whilst with the Terrors last season.
Russell was out for two months on that occasion, with his absence this time around estimated to be six weeks.
However, during that spell Derby have just four Sky Bet Championship matches owing to the October and November international breaks.
Russell will miss the games against Watford (October 19), Birmingham (October 26), QPR (November 2) and Sheffield Wednesday (November 9), and it is hoped he will return to action, if all goes according to plan, towards the end of November.
Since joining the Rams in June, Russell has scored five times in 12 appearances.
He joins midfielders Paul Coutts (dislocated kneecap), Jeff Hendrick (ankle) and James Bailey (knee) as well as goalkeeper Adam Legzdins (ankle) on the list of absentees.