Verdasco will play for the title against unseeded Canadian Milos Raonic, who advanced to his first ATP Tour final in a walkover after second-seeded Frenchman Gael Monfils withdrew from the tournament with a left wrist injury.
Verdasco needed one hour and 36 minutes to beat del Potro, the 2009 US Open champion who was playing in his first semifinal since wrist surgery derailed his 2010 campaign last May.
Verdasco broke del Potro's serve in the opening game of the match and cruised through the first set.
Del Potro mustered a break early in the second, but Verdasco responded and then earned the decisive break to lead 5-4 before serving out the match with a love game punctuated by an ace.