He misses out on most of the preseason anwyay. Plus, I think that he didn't really know it was going to bother him that much until he got back on the field.
Based on what I have read and heard, they originally thought this could be treated medically without surgery, which they have been doing since February. I think that they simply got to a point where it was do it now or risk problems during the season and the risk what is a Colts fan worst nightmare, surgery during the season. He'll be ready.