Another angle on this one. Talking to someone (not from the club, but having business contacts within the club), he told me that Marshie was set up to go to Everton last week until they discovered he has a long standing hernia problem. This is operable but the recovery time is not certain and could well be outside the transfer window.
Having lost Howard for a while through injury they do not want to risk paying a sizeable fee for Marshie (who can play through the injury) only for the injury to get worse and lose him as well. Makes sense.