The reason coaches put their best shooters on the floor for final offensive possessions is because it makes the defense respect numerous options. Having said that, the difference in field-goal percentage between contested shots and open ones is substantial. The Spurs needed to get the highest percentage shot possible on their final play. What they got, however, was one of the lowest. Brent Barry, closed out by Derek Fisher, off one dribble, off-balance, with a release point from his waist? Just guessing here, but only a couple of those out of 100 go in.
In situations like this, since a team has already put its best shooters onto the floor, it matters less who shoots the ball, but rather how open they are, i.e., the highest possible probability of making that shot.
2.1 seconds are enough to catch and make a pass for a rhythm 3 to win. Fisher made an aggressive rotation that could have turned into a monumental error in judgment. He raced to Barry on the inbounds pass, completely leaving Michael Finley on the right wing, who was moving perfectly into that rhythm 3 on the right wing (see photo below, taken with 2.0 seconds left). Barry absolutely needed to make that pass to Finley, who shot 37 percent on 3s during the regular season and is at 35 in the playoffs. Those numbers, of course, are for all 3s. I'd like to think they're higher for open ones, ones where nobody is within 15 feet of him.
Regardless of the exact number, I'm certain Finley is stroking that shot at better than a 2 percent clip. One trademark during the Spurs' successful run is their ability to runs plays such as this to give themselves the best chance to win. Do they always win? Of course not. But if a team puts itself in the best position possible time and time again, it will come through more often than otherwise, and more often than its opponents who lack such precision.
With its season essentially on the line in Game 4, the correct shot for the Spurs was Finley, based on how the play developed.