Torres has left the Spain camp because of a persistent problem with his left ankle. Despite training in recent days, the forward has been released so he can concentrate on his recovery.
The Spanish Football Federation (RFEF) said its medical team had remained in regular contact with Torres' club, Paris Saint-Germain, before the decision was made.
"Due to the persistence of the symptoms, the decision was made to withdraw him from the squad to prioritise his recovery," the RFEF said.
Espi, meanwhile, has earned his opportunity after making a major impact for the Under-21s in their 13-0 win over San Marino on Thursday.
The Real Madrid youngster scored five goals and provided two assists in a remarkable individual display, prompting Luis de la Fuente to bring him into the senior squad.
Spain will host the Czech Republic in Oviedo on Saturday before travelling to face Croatia on October 6.