Very simple criteria: any player whose spot on the final roster is in jeopardy has zilch trade value. The rest of the league has eyes and ears.
There may be extremely rare exceptions when a team is willing to offer a 7th if they really like a particular player and want to dodge a waiver wire fight, but those exceptions are too bizarre and unpredictable to contemplate.
There may be extremely rare exceptions when a team is willing to offer a 7th if they really like a particular player and want to dodge a waiver wire fight, but those exceptions are too bizarre and unpredictable to contemplate.