The Barcelona defender earned a call-up after injuries to Diego Costa and Cesc Fabregas for Saturday's friendly which is set to go ahead despite criticism from human rights groups
Vicente del Bosque's men are the reigning World and European champions and currently sit atop the Fifa Ranking.
Equatorial Guinea, meanwhile, are 119th and without a victory in five matches. Their highest ranked opposition in that run was Tunisia, who sit 47th.
The outlook, then, is not good for the hosts, as they welcome a Spanish side who have lost just one of their last 32 fixtures - a 3-0 defeat to Brazil in the Confederations Cup.
The African nation finished bottom of their World Cup qualifying group without recording a single victory, while Spain edged out France to progress automatically from the European campaign.
Diego Costa - Atletico Madrid's Brazil-born forward who was tipped to make his debut for Spain - has been forced to withdraw from the squad with a torn muscle in his right leg, and he joins Cesc Fabregas (knee) on the sidelines.
Fernando Llorente and Marc Bartra have been called up as replacements, with the latter hopeful of making his senior debut on Friday.
Saturday's friendly is set to go ahead despite pressure from human rights campaigners, who are calling for action to be taken to help 75 per cent of Equitorial Guinea who are gripped in poverty.