The Pats used their depth on the D-Line to improve their 2010 draft. They sent Le Kevin Smith to the Broncos, along with a 7th round pick. In return, the Patriots received a 5th rounder. But one of the conditions of their deal for Derrick Burgess was that if they could acquire a 5th round pick, it would be sent to Oakland instead of a 4th rounder.
So in effect, the Pats used a DE that was likely to be cut, to upgrade a 7th round pick into a 4th rounder.