Everton's board last year committed the club to moving out of the city of Liverpool to nearby Kirkby, where a new stadium is planned as part of a new retail park centred on a massive Tesco supermarket.
The development is opposed by neighbouring local authorities and an inquiry to decide whether it can go ahead is due to reach a conclusion next month.
Everton insist they will still be able to raise the money needed for the new stadium but the loss of such a substantial source of projected revenue is significant for a club with rising debts that is actively seeking a new financial backer.
The redevelopment of the training ground for housing was initially blocked by Liverpool City Council last year. That decision was upheld on appeal on Wednesday by a government planning inspector.
Everton's plans to move outside of Liverpool are controversial but the club's directors feel they have no option because the subsidies involved in the Kirkby development makes it a far cheaper option than building a new stadium in the city.
Liverpool have been forced to shelve their plans for a £400 million new stadium near to Anfield because of the ongoing problems in the wider economy.
Both clubs have consistently ruled out sharing a new stadium, with fans groups from both sides of the city united in their opposition to such a solution.