user: Question: Who had a transfer fee of Released and played the position of DF?
Columns: ['Exit Date', 'Pos.', 'Player', 'To club', 'Transfer fee']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['1 July 2008', 'DF', 'Garry Breen', 'Hereford United', 'Free']
SQL:

assistant: SELECT "Player" FROM "Table" WHERE "Transfer fee" = 'Released' AND "Pos." = 'DF';