There were a few surprises in Spain's list for this summer's tournament, namely Nacho Monreal's inclusion over Chelsea's Marcos Alonso.
However, during his press conference, Lopetegui first addressed Morata's absense, saying: "We are very sorry that there are players who won't be able to come, like Morata and [Marc] Bartra.
"They will not be there unfortunately, but we have made the list thinking it is the one that can help us the most in the World Cup in Russia.
"Morata could have come like other team-mates, but it has not been like that. They have convinced us more, there is nothing else to it.
He continued: "We've opted for three other team-mates who have other conditions. Taking four players in that position is not something we wanted to do. It's a footballing decision.
"Iago can play centrally and out wide, Rodrigo can play in three areas and always has a great attitude with the team. Diego Costa brings a lot of competitiveness."
Turning his attention to Monreal, Lopetegui added: "We are convinced [he] will help us. He is a player that we know and we have decided that he will be with us for what we know about him and what he can contribute.