Goodwillie should be starting every game in the absence of Kazim-Richards, I'm not surprised he's had enough.
He's not the prettiest to watch and will always be held back by the lack of any standout physical attribute, but he does have something about him. You could tell he was rusty as hell against Leicester but still managed to turn a defender inside out and was unlucky not to score. Comes on against MK Dons and makes a difference again.
I assumed there was a fitness reason why Edinho was being selected ahead of him, but it appears from his comments that isn't the case.