Spain coach Fernando Hierro believes his team are similar to the one that won the 2010 World Cup.
A 1-0 win over Iran saw Spain move top of Group B, putting them on track to reach the knockout stage.
"It's a similar group, know that you can't have clones unfortunately," he told Onda Cero.
"But we have a backup group pushing for places every day. That is the only way to avoid relaxing, by having a group of team-mates that push you closer to the limit every day.
"And we have [Cesar] Azpilicueta, [Nacho] Monreal, Saul [Niguez], Koke, [Alvaro] Odriozola, Iago Aspas, Rodrigo and Thiago [Alcantara]. They don't allow the others to rest.
"It's beautiful to see them training and they can be important at any moment."
Spain only need a point against Morocco Monday to seal their spot in the last 16.
