Lucas Radebe, Simon Johnson, Jamie McMaster and Harpal Singh are the more well known who will head the exodus.
Blackwell, who has already presided over the departure of 17 players since taking over, will trim the squad further by not renewing the contracts of many of his young players.
Blackwell said: "We had a cull last season for different reasons, and this is the second wave. I feel all those going have reached their peak at Leeds and need a new challenge if they are to develop their careers further.
"Some of the boys have already left and hopefully they will go on and prove me wrong. It's never easy telling players they are surplus to requirements, but everyone who leaves Leeds goes with our best wishes."