Having already used their three substitutes, Spain played the 30 additional minutes with 10 men, although, incredibly, some of the Irish team admitted afterwards to being unaware of their numerical advantage.
"Mentally we were very strong - this is a mature team," said skipper Fernando Hierro, who accused Ireland of a tactical error during extra time.
"We did have to suffer in extra time because they continued to play a long ball game. Maybe that was a mistake on their part, though, because we dealt with that threat very well.
"This victory will give a real boost to our morale. It will make us stronger."
Spain hobble on towards Saturday's quarter-final against Italy or South Korea with three players on the injured list.
While Raul has a decent chance of getting fit, Albelda is definitely out after aggravating an old groin injury.
Luis Enrique may also struggle to be fit after playing through the pain against Ireland with a leg muscle strain.