Hierro, who had a spell in charge of Real Oviedo in the 2016/17 season, steps in after a day of high drama in the Spanish squad, with Lopetegui and senior players all staging meetings with Spanish FA chief Luis Rubiales.
"All of the Spanish coaches would like in the future to become national team manager".
Lopetegui had signed a contract extension until 2020 just last month and Rubiales is reportedly angry at only being informed of his decision to join Real minutes before the European champions made the announcement public. We have to work on a series of decisions that come two days before the beginning of the World Cup.
Rubiales said the players, who Spanish media said had tried to dissuade him from such drastic action, had vowed to give everything for the team. Maybe this is tough now, but in the end it will make us stronger.
Rubiales travelled from Moscow back to the Spanish training base in Krasnodar late on Tuesday, confirming Lopetegui's departure at a press conference the next day.
"There's a lot to do".
However, as of this morning, Lopetegui has been informed that his services are no longer needed by the the Spanish worldwide side, 48 hours ahead of their World Cup opener.
"There are somethings more important than the sporting side of things, such as values and how things are done".
"I don't feel betrayed, the problem is that things have been done with the complete absence of the RFEF, which is something (we) can not let go by".
Julen Lopetegui has been sacked as Spain boss just two days ahead of their opening World Cup fixture and one day to the opening of the tournament.
"Not because Lopetegui will be the coach of Madrid for the next three years, which seems like a good and respectable choice".
Julen Lopetegui stands by the bench during an global friendly soccer match between Spain and Costa Rica on November 11, 2017.
"It's really odd, I don't really know what to say", said the Leicester striker.
"But, after five minutes, I saw it in the press and we had to react".
"I feel very close to the players and to Julen", declared Rubiales.