Out-of-contract central defender John McGreal has turned down the offer of a one-year deal with Town and has joined fellow Division One side Burnley on a three-year contract.
The longer deal is likely to have been an important factor in the 32-year-old's decision to move to Turf Moor.
New Clarets' boss Steve Cotterill is pleased with his acquisition: "We are delighted to have John on board at Burnley Football Club.
"John is a great signing and is one of the best defenders in the First Division.
"It is great that he has committed his future to Burnley."
McGreal made 150 appearances for the Blues, scoring five goals. He moved to Portman Road in August 1999 for £650,000 from Tranmere.
He was a member of the 2000 play-off-winning side and a regular during the next season's UEFA Cup qualification.
Over the last couple of seasons he has spent lengthy periods on the sidelines due to knee injuries and that - as well as financial considerations - may have had some bearing on the Blues offering him a shorter term contract.