The former Liverpool and Millwall stopper Warner has been pushed out of the first-team fold at Craven Cottage and could move away.
Marshall is in a similar situation and he could move in on loan for a season to boost Wednesday's Scottish contingent.
Plymouth's Romain Larrieu and Birmingham's Nico Vaesen have also been linked in a busy day for The Owls in the press.
Paul Sturrock's first choice goalkeeper is Liverpool's Scott Carson but the prospect of the England player coming seems more unlikely by the day.
In other news, Wednesday's match with Leeds has been moved from Saturday 26 August to the Sunday so it can be shown live on TV.