O'Hanlon is set to make his first appearance at stadium:mk since being released at the end of the 2010-11 campaign when current club Carlisle tackle the Dons on Tuesday night.
During his time at the club, the defender made over 150 league appearances and scored the second goal in the club's 2-0 victory over Grimsby in the 2008 Johnstone's Paint Trophy final as they won their first piece of silverware
And Robinson has revealed his torment at having to let the now 30-year-old to leave.
"He's a great fella and probably the hardest decision of my managerial career was releasing him on a free transfer, the day after the play-off defeat to Peterborough," Robinson told the club's official website.
"He gave his heart and soul to the football club, but we were moving on to other things and, financially, we couldn't afford to give him a new deal.
"I'll never forget coming in that day and having to do that. It's still something that hurts me because he's a good man and I would go as far to say he's the best centre-half the club's ever had.
"We paid quite a bit of money for him and at that time I think he was one of our biggest signings.
"He did really well that year under Martin Allen and then he found a mate called Danny Swailes and if you asked any MK Dons fan to write down a back four those two would be at the heart of it.
"He scored one of the most iconic goals in the club's history, off his nose, his stomach and his knee into the goal at Wembley.
"One thing I'll know about Sean, when the ball is in the air and he's made a decision to go up and get it, everything's coming with it and you're likely to get knocked back a long way."