Blackwell believes at least 10 new players will be needed to strengthen the squad for Division One football.
He said: "I think there will be about eight players left if the players we believe will go, do go. That means bringing in between 10 and 14 players. To try and bring in that amount causes problems with integration, understanding and everything else.
"Whoever comes to Leeds United has to learn they are playing for a massive club, so psychologically you have to look at the players and hope their profile and fitness fits the Leeds United bill.
"It's going to be a tall order getting the right people in for whoever gets the job, and it has to start quickly.''
He said: "I think there will be about eight players left if the players we believe will go, do go. That means bringing in between 10 and 14 players. To try and bring in that amount causes problems with integration, understanding and everything else.
"Whoever comes to Leeds United has to learn they are playing for a massive club, so psychologically you have to look at the players and hope their profile and fitness fits the Leeds United bill.
"It's going to be a tall order getting the right people in for whoever gets the job, and it has to start quickly.''