Anyone who had Brett Myers last year knows the horror of a top SP turned closer. In fantasy I am one of the belief that you should not pay for saves, so having a 200 inning 200 K starter turned into a closer is sad, even if they are solid closers. In Smoltz's case he has been one of the true elite closers when he pitched as a closer in the early 2000's. Also what hurts most is the fact that you had to draft these guys somewhat early last year for Myers and this year for Smoltz. You expected them to be key cogs in your rotation.
None of this is set in stone, and even though John Smoltz said he would be happy as a Closer, it is evident that ultimately he wants to be a starter again. Bobby Cox likes him as a starter too. For the time being Smoltz is on the DL so you will want to stay updated here with this situation.
Also you have to consider what this means for the struggling Manny Acosta and for those people still holding onto Rafael Soriano. If Smoltz closes then these guys lose all of their value of course.
As far as the rotation, this gives a young stud like Jair Jurrjens an opportunity to step up. He has done so up to this point but they need him now more than ever.