No question Todd's the better pitcher and, in my opinion, the Reds' MVP to date.
However, Weathers has been serviceable, with a 3.24 ERA.
There are plenty of teams in the league that have setup men with better ERA's then their closers. I don't think your closer necessarily has to be your best relief pitcher. He has to be able to get the job done, however. I just don't think Weathers will do as good a job as a setup man as Coffey, and we don't yet know how Coffey will react to being "the guy."
Hopefully the move works and Weathers doesn't react negatively to this change.