An review will now be carried out to find the best way forward, as the club look to look to hang on to their best players in order to mount another charge at promotion.
Ben Davies and Chris Humphrey have already been lost to Notts County and Motherwell respectively, while star striker Grant Holt is understood to be close to joining Norwich.
Speaking about Bickerton's departure, chairman Roland Wycherley told the club's official website: "Rob has left by mutual agreement and we will not be making further comment other than to thank him
for his efforts during his time with us.
"This is an important stage in the club's development, so the board will take this opportunity to conduct a thorough review of all off-pitch operations and staffing.
"It is now two years since we moved to the new stadium and it is vitally important that we maintain momentum and develop the business so that it provides the necessary resources to succeed on the pitch."