The defender's current deal is due to expire next year and rather than risk losing him on a Bosman free transfer, Rangers will look to sell if he does not agree to a contract extension - and the indications are that he won't.
Shittu's former club Charlton are entitled to 25% of any transfer fee as are the Winton family, who funded his £350,000 signing in 2001 and plan to reinvest in the club with the cash.