Chelsea midfielder Mata was a member of the Spain team who won Euro 2012, coming off the bench in the final to net the last goal in their 4-0 triumph over Italy.
Mata was also a member of Spain's disappointing team at the London Olympics but, despite an impressive start to the season for his club, was left out of the next three squads.
The 24-year-old missed the friendlies against Puerto Rico and Saudi Arabia, and their opening World Cup qualifiers against Georgia, Belarus and France.
Del Bosque was asked if playing abroad was a handicap for players' chances of getting into the national team.
"We have three players from abroad, Javi Martinez, Santi Cazorla and Mata in this squad," the 61-year-old told a news conference in Tenerife.
"We are always aware of them, and if we have done well recently it is because young players have gone to play outside the country.
"Look at Cesc Fabregas, who at 18 or 19 was captain of Arsenal. It has enriched our football and has been good for everyone."
Del Bosque omitted a number of stalwarts such as Gerard Pique, Xavi, Xabi Alonso and Fernando Torres while giving Athletic Bilbao's attacking midfielder Markel Susaeta and Barcelona defender Martin Montoya opportunities.
"We would like to take more players, but there is no point making changes for the sake of it," Del Bosque said.
"We have a stable squad which is very difficult to improve upon, but we are obliged to give chances to Under-21s players such as Montoya, and another such as Susaeta for other reasons.
"He has played very well at the top level for two or three years, and it is good that he joins us."
The world and European champions take on Panama in the Rommel Fernandez stadium on November 14.
Goalkeepers: Iker Casillas (Real Madrid), Victor Valdes (Barcelona).
Defenders: Sergio Ramos (Real Madrid), Raul Albiol (Real Madrid), Juanfran (Atletico Madrid), Jordi Alba (Barcelona), Martin Montoya (Barcelona), Javi Martinez (Bayern Munich).
Midfielders: Sergio Busquets (Barcelona), Santi Cazorla (Arsenal), Cesc Fabregas (Barcelona), Andres Iniesta (Barcelona), Benat Etxebarria (Real Betis)
Forwards: Jesus Navas (Sevilla), Pedro (Barcelona), Markel Susaeta (Athletic Bilbao), Roberto Soldado (Valencia), David Villa (Barcelona), Juan Mata (Chelsea).