user: Question: What was the manner of departure for the appointment date of 21 September 2010
Columns: ['Team', 'Outgoing manager', 'Manner of departure', 'Date of vacancy', 'Replaced by', 'Date of appointment', 'Position in table']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Valladolid', 'Javier Clemente', 'End of contract', '31 May 2010', 'Antonio Gómez', '23 June 2010', '18th (in La Liga )']
SQL:

assistant: SELECT "Manner of departure" FROM "Table" WHERE "Date of appointment" = '21 September 2010';