Aberdeen manager Derek McInnes said the Dons made Peter Pawlett a strong offer to remain at Pittodrie but were unable to persuade the midfielder to sign a new deal.
The 26-year-old will join Robbie Neilson’s MK Dons in the summer after agreeing a two-year contract with the English League One club.
Pawlett has scored 20 goals in 207 appearances for the Dons but has started only five games in the league this season.
McInnes said: “We’re disappointed to lose Peter. He’s the first one we’ve really wanted to keep but who has decided to move on.
“I respect his decision to go, his reasons are that he wants to play in England.
“We tried hard to keep him, we offered him a two-year deal and a testimonial.
“I thought the testimonial, the chance to play in Europe and the chance to play in cup finals would sway it but, in the end, it wasn’t enough.
“We worked hard and showed a desire to keep him but he wants to try England and we respect that.
“It wasn’t about lack of opportunities, that wasn’t mentioned, what he did say was he wanted to play down south.
“He’s liked what he’s seen at MK Dons and believes that’s where the next step in his career is.
“He will still have a part to play in helping us achieve what we want to this season. He was a big part in the upturn in fortunes over the last few seasons, especially in those first few years.
“I still believe he’s got more to come in his career and was hoping that would be with Aberdeen. But he’s made the decision and we will wish him well when he goes at the end of the season.”
Captain Ryan Jack, Ash Taylor and Niall McGinn are also out of contract at the end of the season – and McInnes hopes they won’t follow Pawlett’s lead and depart for a new challenge elsewhere.
He added: “We have managed to maintain the majority of players but there are the three who are out of contract in the summer.
“All three of them are playing particularly well, they are big players for us.
“I want all three to stay, I have made that clear that I want to them to continue their development and careers with us.
“They are quite within their rights to consider everything but hopefully we can get some sort of clarity in the next week or two and see where we go.”