Irish midfielder who signed for Town less than a week before the beginning of last season, joining from fellow Championship side Brentford.
The central midfielder, who often captained the Bees, scored three times in his debut season for the Blues.
As well as bringing a wealth of experience to the squad, Douglas made his name as tenacious midfielder whose work rate has always been a huge asset to the team.
He has been capped eight times by the Republic of Ireland and made his Blues debut against former side Brentford, on the opening day of the season.
Player kit sponsor: Absolute Audio Visual Solutions LTD