Before you go into too much detail about who screwed up last night, consider this. The Spurs lost that lead in just 3 minutes of play. The lineups on the floor when it happened were Parker, Green, Leonard, Bonner, Splitter and Neal, Green, Jefferson, Bonner, Duncan. So you can't blame it all on one group of players.
It's pretty simple. The Pistons dialed up their defensive effort, a few calls went against the Spurs, and for just those few minutes, the Pistons scored at a 220-point game pace. Also during that time, the Spurs offense went totally stagnant. They wound up taking mostly taking desperation shots, late in the shot clock. To be more specific, their shots were put up at 26, 21, 24, 19, and 23 seconds into the clock. (The one non-desperation shot at 19 seconds was where Duncan got his arms almost ripped off by Wallace, and then got elbowed in the eye.)
We're talking 3 minutes, from 10:44 to 7:47. During that time, Detroit got 2 and-1's plus two 3-pointers from guys who aren't good 3-point shooters. There was also a jump ball that Jefferson "won" but hit out of bounds. And there was a possession where Tiago blocked a shot by Ben Gordon, 22 seconds into the shot clock - but the ball went out of bounds and back to Detroit, and Ben Freaking Wallace hit his 7th career 3-pointer. That was a very good defensive possession, ending in disaster.
In short, it was something of a perfect storm - for 3 whole minutes. Before that, the Spurs kicked Detroits collective asses. After that, even though the Pistons had confidence, you didn't really have the sense that they were going to be able to win the game.
So how did the Pistons defense get the best of the Spurs for those 3 minutes? My opinion is that it came down to two things.
1. The Spurs quit moving without the ball.
2. The Pistons were doing something that has been making me crazy this year, all over the NBA. (Not just against the Spurs.) They were "hedging" out around the 3P line. Only the hedges consist of actually putting a body on the ball-handler and physically shoving him toward mid-court. And at the same time, they were getting into the passing lanes to the guys sitting still in the corners.
I don't blame the Pistons for doing it. But I do blame the NBA for letting the practice get out of hand this year. A hedge is a hedge - but a shove, even if done with the body, is still a shove. But I blame the Spurs players the most, for sitting on their asses and not doing anything to help out the ball-handlers.