Colchester announce that captain Brian Wilson has left the club after rejecting a new contract.
The 30-year-old joined the U's in the summer of 2010 and has been a regular over the past four seasons, making more than 160 appearances.
Colchester were keen to retain the defender's services but he has decided to move on.
U's boss Joe Dunne said: "I did try and keep Brian but I understand that it can be a difficult situation.
"We are in a financial market where there are other clubs able to pay players more than we do. When that situation arises, you have a decision to make.
"He's got a young family and is from a different part of the country and has decided he wants to move.
"I fully respect Brian's decision, he's been great for us and he was my captain. We tried to keep him but wish him all the best in the future."