The initial hope was that the fraying of the cartilage could be taken care of through arthroscopic surgery, but once surgeons started, they realized more needed to be done.
While the recovery will be longer than expected, both manager Kirk Gibson and acting general manager Kevin Towers said they expect Ziegler will be ready when Spring Training starts next year.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.