The 27-year-old was listed as the Spanish squad's third keeper after Real Madrid's Iker Casillas and usual substitute Jose Reina of Liverpool.
"We must have a perspective that that goes a bit beyond this call-up and we thought it would be a good idea that we be covered during these two games against the possible injury of a goalkeeper," said Del Bosque.
Lopez was Casillas' understudy between 2005 and 2007 when he was at Real Madrid. He is the only new name in the squad unveiled by Del Bosque.
"To say this is the group which is going to the Confederations Cup in South Africa when there are still a few months to go until the event would be an unnecessary judgement on my part," said Del Bosque.
This year's edition of the FIFA Confederations Cup will take place between June 14-28 and it features Spain, Italy, Brazil, New Zealand, Iraq, USA, Egypt and hosts South Africa vying for the title of 'champions of champions.'
The European champions have not lost a game since going down 1-0 in a friendly to Romania in Cadiz in November 2006.
They top their qualifying group, with four wins from four games, and have only conceded one goal in their last teninternationals.
Goalkeepers: Iker Casillas (Real Madrid), Jose Reina (Liverpool/ENG), Diego Lopez (Villarreal)
Defenders: Raul Albiol (Valencia), Alvaro Arbeloa (Liverpool/ENG), Joan Capdevila (Villarreal), Juanito (Real Betis), Carlos Marchena (Valencia), Gerard Pique (Barcelona), Sergio Ramos (Real Madrid)
Midfielders: Xabi Alonso (Liverpool/ENG), Sergi Busquets (Barcelona), Xavi Hernandez (Barcelona), Andres Iniesta (Barcelona), Marcos Senna (Villarreal), Santiago Cazorla (Villarreal), Albert Riera (Liverpool/ENG), David Silva (Valencia)
Strikers: Fernando Torres (Liverpool/ENG), Daniel Guiza (Fenerbahce/TUR), David Villa (Valencia), Fernando Llorente (Athletic Bilbao)