The Roja coach insists that the Atletico Madrid ace has a bright future with the world champions, even though he was uninspiring on his first appearance for his adopted nation
The Atletico Madrid striker failed to make an impact in Wednesday's 1-0 win over the Azzurri at the Estadio Vicente Calderon, with Pedro scoring the only goal of the game for the hosts.
However, Del Bosque has little doubt that Costa, whose inclusion was the subject of much controversy given he had previously represented his native Brazil in two friendlies, will improve once has has got used to his new team-mates and their style of play.
"All of the players have become stronger and we've brought in Diego Costa, who we feel will gradually adapt to the team's style," the Spain coach told reporters.
"None of the players can be detrimental to Spain's style and I thought Diego looked comfortable. He looked stable considering it was his first game but, once he loosens up, I'm sure he'll being a lot to the team."
Pedro's 63rd-minute strike saw La Roja emerge victorious and Del Bosque was generally pleased with his team's performance.
"We moved the ball around well and we were slightly superior to Italy. Given it was a friendly, we had some very good moments," the former Real Madrid boss reasoned.
"We had some spells of great play, even though they too had their chances. We were lively with our play, we made the ball do the work and our circulation was good. We were also attentive defensively when they attacked."