Donnie Marshall being gone doesn't really surprise me.
Though obviously I have no knowledge of this, sometimes Marshall wasn't afraid to "speak his mind" without the green-colored glasses.
Case in point, I remember vividly the tussle with Brooklyn last year (ironically now our teammates) and Marshall was VERY critical of the way Rondo handled himself in that melee.
Can't help but wonder if it's reasons like that why his contract wasn't picked up.
Also, to a much lesser extent, I think the same can be said for Tanguay and Dickerson. Though both guys have always been pro Celtics, they're also not always afraid to tell things the way they see them.
Make a long story short, my theory here it's quite possible the Celtics are going to be absolutely horrendous this year and if so, they don't want any "objectivity" behind the mic.