Twelve first-team players were put up for sale in the wake of Posh's promotion to the Championship and Liam Hatch has already agreed a season-loan move to Luton.
"I feel absolutely certain there will be interest and offers for every single player that we put on the transfer list, but whether they choose to accept those offers is a different matter altogether," Fry told the Evening Telegraph.
"Some of the lads might think that they will get an opportunity in the Championship if they hang around long enough, but in all fairness that is not going to happen.
"The majority of the players we made available are young so I would encourage them to get out there and play football because that's not going to happen here.
"It won't do them any good being sat in the stand for a year."