The relegated Hammers have a number of assets in their possession at present but the former Blackburn Rovers, Bolton and Newcastle United boss can see these key players, headed by midfielder Scott Parker, to say goodbye to Upton Park in the current transfer window.
"I don't know if I'll be able to keep Parker. We'll have to wait and see but it looks like it will be difficult," he said.
"I've not spoken to Scott about it, but I've talked to David Sullivan and there have been no indication of bids for him yet.
"There will probably be an exodus of top players for financial reasons. There's a dramatic loss of revenue, even with the parachute payments, and you have to adjust, like every club does.
"But whatever happens with some of the big players there's the basis of a good squad and some very, very good young players to rebuild quickly.
"The transition needs to be quick and how big that is we won't know until nearer the start of season.
"The board have said they'll back me as best they can from a football and a financial point of view to get back into the Premier League."