Fernando Morientes came off the bench to send Spain through to the last 16 of the World Cup with two goals against Paraguay.
Morientes came on at half-time to grab his priceless haul - he also hit the bar - with Hierro adding the third from the spot.
Spain produced a complete turnaround on their first-half display, which had seen Paraguay go in at the break deservedly ahead.
After getting the start they desperately wanted by beating Slovenia 3-1 in Group B, Spain needed to build on that result.
But Paraguay had done their homework and the wily Italian coach, Cesare Maldini, set up his team to exploit the slowness in Spain's defence and the gaps created by Francisco De Pedro's left sided midfield assaults.
The goal Paraguay had been threatening from the off came on ten minutes.
Ruben Baraja was booked for a foul on Carlos Paredes, the Porto midfielder, and from the free-kick the South Americans got their noses in front.
Two half-time substitutions helped Spain regain control, with Morientes bringing on Ivan Helguera and Morientes for Tristan and Enrique.
And it worked, with one of the two Real Madrid new boys grabbing a 52nd-minute equaliser.
De Pedro's corner was met with a towering header from Morientes, climbing above a host of friends and foe, to power the ball past Chilavert.
The Spanish went ahead on 68 minutes when De Pedro crossed from the left again, Chilavert made a real hash of taking the cross as Raul rushed in, and the ball sailed on to hit Morientes and bounce into the net.
And it was settled on 81 minutes when Raul was pulled down in the box by Parades and Hierro stepped up to drill home the penalty, equalling the Spanish goalscoring record in World Cup finals - his fifth.
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