The sixth seed overpowered the Spaniard in two hours, 20 minutes of outstanding hitting to set up a final against either five-times champion Roger Federer or fourth seed Novak Djokovic of Serbia.
The first set was a story of missed opportunities as Nadal squandered three break point chances, while the Argentine broke twice, in the fourth and eighth games.
The pattern was repeated in the second set and though Nadal continued to fight in the third, Del Potro was too strong and cruised to a comprehensive victory.