There are more problems than just having new guys. The real problems are 1) the decline in play from TP. 2) health 3) integrating the new guys into the system and 4) rust.
Those things in order are the real reasons. As I mentioned before, plenty of teams have a lot of new guys to acclimate into their systems. The thing that is catching Spurs fans off guard is their jaded view of where the Spurs were at coming into the year.
Many fans sorely over-estimated how close the Spurs were last year. The Spurs, out of all of the "contenders" have the most question marks. You are seeing this now. These things can be corrected, but unlike many other teams, the Spurs have to have a lot of things go their way just to have a shot.