Much was made of the striker's decision to snub Brazil, the country of his birth, in favour of representing Spain, but he has scarcely made an impact since his debut against Italy in March.
Spain's torrid World Cup campaign, during which Costa made two scoreless starts, brought the forward's form into sharper focus as many questioned his role within Del Bosque's system.
But the coach backed the Chelsea man, who leads the Premier League scoring charts but is currently out injured, to make his mark for the European champions.
"I believe that a player who plays great in his club – both Atletico Madrid and Chelsea – cannot be damaging to the national team," Del Bosque told FIFA.
"I'm convinced that in the next matches he will settle in to the group. He will adapt to the group and the group will adapt to him."
Costa's next chance to impress for his country will come in November when Spain host Belarus in a European Championship qualifier, before welcoming world champions Germany in a friendly.
The 26-year-old has won seven caps, with his only goal coming in October's 4-0 victory over Luxembourg.
