Del Bosque hails Costa
The Brazil-born Chelsea star scored his first goal for Spain in a 4-0 thrashing of Luxembourg in a Euro 2016 qualifier.
Del Bosque lauded the 26-year-old, and said the striker had impressed throughout his seven-cap Spain career.
"[He] is truly giving his all; he wishes to pay us back for all the support we gave him," Del Bosque said.
"He feels comfortable with this group of players and we appreciate his efforts and the way he makes himself available on the pitch. He combined well with Paco Alcacer, who needed to find space.
"During the half-time break, I told him to stay focused because if he kept calm he would get a lot of satisfaction. We noticed he was upset with his performance.
"He was getting frustrated because he couldn't finish, but when a player puts in as much enthusiasm as he did today, he eventually gets what he desires."
David Silva, the in-form Alcacer and Juan Bernat were also on the scoresheet for Spain, who sit second in Group C.
Del Bosque made several changes to the team stunned by Slovakia on Thursday, including bringing in David de Gea to replace Iker Casillas in goals.
He said the plan was always to gradually make the Manchester United goalkeeper his number one.
"I would not like to make a difference between them and the rest of the team," Del Bosque said.
"We knew we were going to make some changes and we wanted to have a smooth transition in the goalkeeping position.
"That means that Iker will facilitate and David will start fitting into the team slowly, as long as both play regularly for their clubs."