The 27-year-old Irishman will exit Elland Road after nearly four years this summer when his current deal expires.
And the former Blackburn man has expressed his sadness at first captaining the side that lost in last season's play-off final, and secondly being part of the team that lost to Millwall at the semi-final stage this time around.
"I've had four years at Leeds, I enjoyed my time there and it will be obviously a wrench leaving the club," he told Leeds' official website.
"The fans have been great with me and I'd like to take this chance to thank them for all their support. They have stayed with the club through everything, turned up in numbers, and backed us to the hilt.
"The biggest disappointment is that we couldn't reward the fans with something to celebrate for their support. Losing the play-off final to Doncaster after coming from 15 points behind was a bitter disappointment, as was the semi-final defeat against Millwall last week."