Ryan, pivotal to the Spireites’ success in the past two years, was set to be out of contract and on Wednesday signed a two-year deal with Fleetwood on a free transfer.
Chesterfield wanted to keep the central midfielder and matched the offer on the table from the Cod Army, but Ryan wanted to relocate back nearer the north west where his family is based.
Turner said: “Jimmy made a great contribution during his time with us and was an important figure when we won the League Two title in the 2013/14 season.
“We are naturally disappointed to see Jimmy leave as we wanted him to stay. The previous management team talked to him about a new contract last season and those talks continued over the last few weeks.
“I am told that we matched the terms offered by Fleetwood, but Jimmy has chosen to go there because it is closer to his family home.
“I would like to take this opportunity to thank Jimmy for his services and wish him all the best for the future.”
Ryan, 26, made 100 appearances for Chesterfield and scored eight goals after joining the club from Scunthorpe in the summer of 2013.