What surprises me the most with this move is that Mason is only 28 years old (seems like he's been here forever). I'm guessing that a couple of things played into this - would he play on his non-guaranteed, cheap contract through next year? or was he going the Gilmore route?
And/or, BB wants money to grab some guys tomorrow and didn't want to have to borrow it all from next year. He probably thinks he can fix the OL "enough" pretty cheaply with the draft and the guys in house - Herron, Desjarlais, Cajuste, Williams, etc. - but needs some $$ for D talent.