He's really more of a 4-3 DE, so moving to the Lions make sense. He's a very poor 3-4 DE which is why the Bears didn't try and re sign him.
Good for him though, he should make a solid DE for them.
So now what at starting DE opposite Hicks? Unrein or J. Allen?
Well Unrein was the starter last year, and there is also Bullard who has had a year to get NFL strong. If they aren't happy w/that then ya they can go dip into the FA or the draft.