The All Star last night completed any hopes of a return, which had been sparked by hints from Jim McGuinness that the door is never fully closed.
However speaking in Irish on TG4 last night, the 30-year-old Gaoth Dobhair half back said he believed he has played his last game for the county.
Dara O Cinneide on the station asked Cassidy: “Have you or Jim McGuinness closed the door on your return to Donegal, is that the end of it?”
Cassidy replied: “That is the end of it, yes.”
He went on: “The season has started, the lads are back in training.
“Even for me, it would have been very difficult to return and put in the same level of effort.”
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