There has been some movement on the Draft boards after the official Combine workouts have been completed. This reflects the needs of teams Pre-Free Agency.
I am using the PFF Mock Simulator, and any trades are made with teams interested and willing to trade, as long as you can make the trade balance out.
Zion Young is selected just in front of the Patriots at #30 by Denver. That prompts the trade down to a team that wants to jump back into the 1st round and get that 5th year option on a rookie contract.