The Italian media have questioned the legitimacy of the striker playing for Spain over the country of his birth, Brazil
The striker is set to make his first appearance for la Roja at the Santiago Bernabeu since making his decision to represent the current world and European champions rather than the country of his birth, Brazil.
That move has provoked much debate and after the Italian media quizzed Del Bosque over the striker's call-up, the 63-year-old hit back by accusing the Azzurri of hypocrisy for their selection of Argentina-born Dani Osvaldo.
He told reporters: "Italy play [Pablo] Osvaldo, right? Was he born in Italy? The argument has passed. Costa is eligible to play for us, legally and technically.
"He's playing well with Atletico Madrid, is a striker who can compete with all the other strikers at our disposal and also has different characteristics from the others."
Del Bosque then discussed the prospect of facing Mario Balotelli and admitted the AC Milan star possesses some considerable attributes that could cause Spain problems.
"He is a unique player, capable of anything and everything," he added. "He is a great player who has a vast array of qualities - goals, strength, speed, shooting. If he wants to be, he can become one of the best strikers in the world."
Juan Mata, Fernando Torres and Fernando Llorente are three high-profile absentees from Spain's squad, with Del Bosque admitting he has some difficult selection decisions to make ahead of the World Cup.
"Juventus were expecting a call for Llorente, but then some might be wondering at Chelsea why Torres isn't with us. The same goes for Tottenham and [Roberto] Soldado, or [David] Villa at Atletico Madrid.
"For Llorente it is important that he has already exceeded anything he did last season with Bilbao, he has continuity at Juventus and he and the club are happy. He knows we appreciate him."