Barcelona have opened a two-point gap at the top of LaLiga table following their 5-0 thumping of Valencia on Sunday.
The Spanish champions watched on Saturday as their rivals Real Madrid lost 1-0 to Real Betis.
Madrid’s defeat presented Barca with an early chance to establish an advantage in the title race.
It was an opportunity that Hansi Flick’s men took with both hands.
Lamine Yamal opened the scoring as early as the sixth minute, before Fermin Lopez made it 2-0 before the break.
In the second half, Raphinha, Pedri and Yamal got on the scoresheet as Barcelona ran riot at the Mestalla.
Barcelona now have 12 points after four fixtures, with Alaves in second place on 10 points.
Real Madrid sit in third position with nine points.