St Johnstone are close to securing Croft's services on loan for all of 2012/13 after the former Manchester City midfielder enjoyed a spell at McDiarmid Park in the latter stages of last term.
And Bournemouth are seeking a permanent deal for Addison, who was loaned to the Cherries in January.
"It looks like Lee will be going back to Scotland," said Derby manager Nigel Clough.
"It will probably be a season-long loan, which would give us the option to call him back in January and do something with another club if the opportunity arose."
Addison impressed during his stint on the south coast, with Bournemouth boss Paul Groves revealing he would like to see the 23-year-old at Dean Court again. The Londoner spent the first part of 2011/12 at Barnsley.
"We're talking with one particular club and that one is getting closer," said Clough on Addison.
Striker Steve Davies and midfielder James Bailey are also said to be heading for the exit door at Pride Park.