From what I have seen, Duncan's game has fallen off dramatically. But there are more contributors on this team than in the last couple years. Manu is now clearly option #1, Jefferson is finally playing like, well, Jefferson, and everyone else is hitting shots. When Duncan can put up a triple double for this team, it is gravy.
The biggest indication that Duncan is in decline happened in the T-Wolves game a week ago. Up by a couple points, with Minnesota holding the ball, Dyess gets substituted in for Duncan, who watches from the bench as his team clinches the win on defense. Never would have imagined I'd see Tim Duncan on the bench when the Spurs are trying to win a game on D.
I'll wait until they are about 30-5 before I start to think this will lead to anything. The Lakers have still got to be the clear-cut favorites, and until the Spurs make a few statements against them and some of the league's other elite teams, I'm going to just consider this a "nice run", and nothing more.