The 21-year-old has played for Spain at age-group level and has been included alongside Real Madrid new-boy Isco and Real Sociedad defender Inigo Martinez.
Cristian Tello, Fernando Llorente and Alvaro Negredo were also included but there was no place for Manchester United goalkeeper David De Gea, Barcelona midfielder Xavi or Atletico striker David Villa.
Del Bosque only named five Barcelona players in his squad - goalkeeper Victor Valdes, defender Jordi Alba and midfielders Andres Iniesta, Manchester United target Cesc Fabregas and Tello.
Jose Reina, who recently joined Napoli on loan from Liverpool, is also included along with new team-mate Raul Albiol and Real defender Alvaro Arbeloa.
Spain will play Ecuador in a friendly in Guayaquil next Wednesday.
Spain squad to face Ecuador: Casillas, Reina, Valdes, Arbeloa, Azpilicueta, Inigo Martinez, Albiol, Ramos, Javi Martinez, Cazorla, Iniesta, Isco, Thiago, Koke, Navas, Silva, Fabregas, Negredo, Llorente, Tello.