Martin O'Neill and Roy Keane are among those being linked with the vacant manager's job at Nottingham Forest.
The Championship club have parted company with Aitor Karanka after just 12 months in charge.
The club said in a statement:
Aitor Karanka has asked to be released from his contract as the manager of Nottingham Forest Football Club.
The club have agreed to this request and the terms of departure have been agreed. Both parties wish each other every success for the future.
There will be no further comment from either party.
Simon Ireland will take charge of first-team affairs until a new manager is appointed.
Reports suggest that the two Irishmen are being considered by the club, including the Nottingham Post newspaper.
Both O'Neill and Keane played under Brian Clough during his legendary reign at the City Ground.