Which position/player has to be the smartest on the pitch?

Soccer is a thinking man's game in many respects. Which players/positions benefit from having someone who is legitimately very smart? I think deep lying playmaker is probably the position that requires the most intelligence. Players who do it well (ie Pirlo) are sometimes responsible for the entire engine of the offense. Without them the attack would stutter. Obviously other positions require intelligent play (like I said, soccer is a thinking man's game), but my vote still goes to the DLP.

I know "intelligence" is a broad and maybe vague categorization here, but this includes all things soccer and non soccer related, from basic IQ to the ability to read the game, predict movements, etc etc.