The Warriors are so good they rarely need help on the margins. When those margins exist, though, Andre Iguodala is the one that addresses them. Witness the 2015 NBA Finals, when Iguodala's defense and timely shot-making earned him the MVP. His importance in that series was obvious. His importance in regular-season games is less so, but it's still there.
Iguodala's defensive style is a remarkable application of game theory in real time. He doesn't just know the scouting report, he also realizes the opponent knows that he knows the scouting report.
For all his athleticism, Iguodala succeeds defensively by coaxing his man into uncomfortable positions. His work on LeBron James in the NBA Finals was noteworthy not because he squared him up and stopped him one-on-one, but because he shaded James into the jaws of the Warriors' stunting defense. He knew James wanted to pass and he knew the Warriors were faking double teams and recovering to their men. By positioning himself appropriately, Iguodala led James to the mouse trap.
Iguodala still plays chess when his assignment plays checkers. Notice his right hand on this sequence defending Paul George, for example.
Iguodala knows George exposes the ball briefly on turnaround jumpers, so he held his hand to the left of George's face. He didn't slap all the way down, because that risks a foul. He just kept his arm there, and it was enough to stop George from even taking a shot. Iguodala makes it look like he's been caught in the cookie jar, only to pull that arm back as his man goes to punish him.
Here's another example on a key late-game switch against Kyle Lowry. Watch Iguodala's left arm as Lowry steps back.
For a split second, Iguodala held that left arm out as if he was inviting Lowry to jump into it to draw a foul. Lowry isn't used to a defender holding his arm that close to him without any contact, so his shot looked more awkward. Better yet, Iguodala raised his arm just enough to contest the step-back properly. Those two factors caused Lowry's shot to carom harmlessly off the rim. Iguodala essentially fooled Lowry into thinking he made a mistake.
Toss in 39 percent three-point shooting, superlative playmaking, excellent pace running up the wings in transition and a willingness to defer, and Iguodala is one of the most unique role players in league history. He's mastered the art so thoroughly that it almost bores him. The Warriors can afford to limit his exposure and let him prop up an otherwise-shaky second unit until games actually matter.
Once they do, they knew where to turn. In tight games, Iguodala rises to the occasion.