The Ardara man picked up a hamstring injury in a club game last weekend against Naomh Conaill.
The strain isn't as bad as first feared and Mc Grath is expected to take some part in training in the coming week.
Donegal's win over Derry at the end of May was McGrath's first game back from a lenghty lay off with a groin injury.
Neil Gallagher came off in the victory over Antrim but the Glenswilly man did return to training last Tuesday while Rory Kavanagh who missed the semi final is also close to a return.
Buncrana's Darach O'Connor and Gweedore's Ordhran MacNiallais pickled up knocks in training this week but both are not serious enough to make them doubts for the provincial showpiece.
Donegal await the winners of the semi final replay between Armagh and Monaghan.