Costa, 28, was not included in Vicente del Bosque's Spain team for Euro 2016 after a stuttering 2015-16 season with Chelsea in the Premier League.

Del Bosque stepped down following Spain's 2-0 round-of-16 loss to Italy in France, with Lopetegui taking over the reins of La Roja. Costa was picked by the new boss for qualifiers in September and October -- scoring twice in a rout of Liechtenstein and and again in a win against Albania -- but missed out on a November win against Macedonia due to injury.

Now on 17 Premier League goals for leaders Chelsea, Costa looks rejuvenated, according to Lopetegui, who is thrilled to have him back with the team. 

He told Radio Marca: "He's calm and happy. He has had a lot of consistency and form at Chelsea and we are all delighted.

"The players who are with us have shown incredible behaviour. The players are the medicine for the Spain team and they will help us achieve our goals."

Spain are in firm control of UEFA qualifying Group G at the moment, but Lopetegui said that neither he nor his players will look past third-placed Israel as they continue the road to Russia 2018.

"The main focus is to get points against Israel. We need to convey the importance of this game," he said.

"They have good players and they are a competitive team. We know how difficult they are, we have to perform well.

"We absolutely respect Israel and I'm sure that they are also going to be respected by the city of Gijon."