Derby have rejected Richard Keogh's appeal against his dismissal for gross misconduct.
Keogh's agent told Sky Sports that the defender will now lodge a complaint to the English Football League, who will make a final decision on the case.
The 33-year-old Republic of Ireland international defender was sacked in late October, a month after suffering a season-ending knee injury while a passenger in a car driven by team-mate Tom Lawrence after a night out.
Lawrence (25) and another team-mate Mason Bennett (33), whose car the former crashed into, were both fined six weeks' wages by the club after convictions for drink driving.
Former club captain Keogh was contracted to the club until June 2021 on a reported £24,000 per week.
He is believed to have refused a renegotiated contract on reduced wages.
Speaking a fortnight ago, Republic of Ireland manager Mick McCarthy said: "I'm astounded at what’s gone on there, I really am.
"If Richard had got in an Uber and the Uber driver was drunk, I don’t think they would have sacked him."