I'm not sure based on the way you phrased the question that I've made the draft process clear.
There is no trading prior to the draft as I define the draft as the selection of the 12 COMBO FRANCHISES which have been identified as #1, #2 & #23 etc. Based on SALARY CAP of each FRANCHISE.
Once all COMBO's have been selected all players on both teams of the COMBO are the managers property. At this point, all players belonging to the COMBO can be traded.