Pitchers don't miraculously regain velocity that they didn't have at the beginning of the season, it just doesn't happen. The Sox(and Koch) may have wanted it to happen but now that push is coming to shove it appears reality is finally starting to set in. The hope now(at least my hope) is that Billy has finally decided to add a cutter and they want to give him some minor league innings to work on it, thus the reason for the DL and the subsequent rehab assignment. If all goes well, Billy can come off the DL in time to be included on the playoff roster. If not, his DL stint will extend beyond Sep 1st and the Sox will have an injury spot to play with.
I also hope that his rehab will be at B'ham so we can get updates from Rex on how he's doing.