Blackwell told Leeds' official website: "Scott Carson has been hotly tipped to be leaving the club and now someone has come in for Aaron. And I am worried that Simon Walton could also be involved, and even my top scorer David Healy is another one I worry about.
"People will look at the club and realise we are vulnerable due to finances and we will have to deal with predators looking to pick off your best players. Just as we are starting to build something here one hopes that we are allowed to continue.
"But it all out of my hands, the board are dealing with finances and I hope they will make the right decision."
The bid for Lennon was rejected and Blackwell added: "We are delighted he is staying here and hopefully that will be the policy of the club should the finances allow it."