Let me say I am not trying to single out Tim as the problem. He has easily been the most consistent and valuable player on the team, and he is still arguably the best big man in the game.
However, he's slipped to the point where teams no longer have to constantly double him. We saw this against the Mavs in last year's playoffs, and we've seen it this yeah as well for the most part.
In the past, failing to double up on Tim basically meant conceding a 35-40 point night on a great shooting percentage.
Now? Most teams elect to play him straight up and give him his 20 or so on 50% shooting. (They are probably especially thrilled by Timmy's move away from the low-post. He's not going to scare teams shooting jumpers all night.) have you watched the last two games there, dumbass?
What is the result? Fewer open threes for limited offensive players. No more swinging it to the weakside for easy buckets after Timmy is doubled. An entire offense built around Tim's ability to draw double-teams is out of sync.
The Spurs now need more creative ways to get their offense going than just dumping it in to Timmy. They can still give him the ball, and he'll score with a decent percentage. But it doesn't propel the entire team offense.
Now we are seeing how badly the team needs a playmaker. It's now clear how much Tony lacks in this area. For so many years, the respect Timmy commanded from other teams was enough to get the offense rolling. The other players did not have to create as much on their own. Their deficiencies were hidden by Tim. Now they are being exposed.
If the Suns didn't have to constantly double Timmy, for instance, the Spurs would have always lost to them.
It's becoming clear how much Tim means to the team, and his decline on both the offensive and defensive end has been a bigger factor in the team's overall slippage than anything else. The Spurs minus Tim now are probably as good as the Spurs minus Tim have been this decade, if not better (in spite of all the complaints). But not good enough to compensate for Tim's decline.