Ronaldinho Gaucho broke the deadlock in what had been an evenly balanced match when he fired home from the penalty spot 10 minutes before the break and completed the rout with an incredible goal to take his tally for the season to 10.
It`s important to mention that the triumph left the champions top with 29 points from 12 matches, four ahead of Sevilla who travel to Athletic Bilbao later yesterday and six clear of Real Madrid who are at Valencia.
In another match, Real Sociedad’s wretched run of luck continued when defender Ion Ansotegi commited an own goal to deny them a first win of the season as they drew 1-1 at Atletico Madrid.
Forward Gari Uranga gave the basement side the lead midway through the first half when he got in between the Atletico centre-backs to send a glancing header past gaolkeeper Leo Franco.
However, just when it looked as though they might hang on for the win Ansotegi chested the ball past his own keeper after winger Luciano Galletti hoisted a hopeful ball into the area 13 minutes from time.
Sociedad remain anchored to the bottom level on five points with Gimnastic, who played Real Mallorca later yesterday, while Atletico stay in fifth spot on 21.
Rijkaard's squad looked far from their fluent best in the opening half hour at the Nou Camp and were given a couple of early scares by Villarreal striker Diego Forlan.
But they got a crucial breakthrough when Eidur Gudjohnsen manufactured a penalty 10 minutes before the break after he flung himself to the ground when defender Pascal Cygan laid a hand on his arm as he turned into the area.
Ronaldinho Gaucho did the rest when he fired the resulting spot kick low past keeper Mariano Barbosa and into the corner.
The goal sparked Barca into life and it took some fine keeping from the fast Barbosa to deny Deco, Ronaldinho and Giovanni van Bronckhorst before the break.
Gudjohnsen, though, found a way past the Argentine early in the second half when he nodded in at the far post after Andrea Iniesta floated the ball across the area following a Ronaldinho free kick.
The stylish Iniesta made it 3-0 with a spectacular finish when he threw himself at a Gianluca Zambrotta cross to volley the ball into the ground and send it skidding into the net.
But the midfielder was outdone, however, by Ronaldinho who put the icing on the cake with his 10th league goal of the season two minutes from time.
Lurking in the area with his back to goal, the Brazilian controlled a neat pass from Xavi with his chest and then looped a perfectly weighted overhead kick beyond the reach of Barbosa and high into the net to bring the whole stadium to its feet.