Mangala has struggled for game time at his parent club, Manchester City, and he had wanted to use the remainder of the season to put himself in the shop window ahead of summer, and potentially make a run at getting into the talent-rich French squad for the World Cup.
However, during last week's win over Palace, Mangala fell awkwardly and was substituted just before half time and there is a fear that he may have suffered serious knee ligament damage.
If it is a cruciate ligament injury then it is unlikely the Frenchman will be able to play again until after the start of next season, while something less serious may give him a fighting chance.
He is still being assessed by Everton's medical staff but things don't look promising for the 27-year-old.