Prior to Miss Start. Headed to the DL?

I have just heard that Mark Prior will not pitch Tuesday. He is headed back to Chicago and will have a MRI on his right shoulder. According to the WGN Radio Crew, Jim Hendry will make his mind up by the end of the game on the status of Prior. I would love to see Cruz pitch Tuesday, but they are saying he would not be on his normal rest. I am sure there will be more later. It would have to rain on the only day I am able to listen to the Cubs all week.