Pere Pons fired straight at Marc-Andre ter Stegen shortly before 1/2-time, whilst Joselu flashed a header huge inside the second 1/2.
The win movements Barca to inside a point of fourth-placed Atletico Madrid, who they host at the Nou Camp next weekend.
Barca appeared weary after again-to-back more-time defeats over the last week, to Real Madrid in the Spanish Super Cup closing weekend and Athletic Bilbao within the Copa del Rey on Thursday.
They loved seventy six% possession and had 10 corners to Alaves' one, however struggled to create many clear-cut openings.
A turgid match gave the look to be drifting to a goalless draw whilst Torres, signed from Manchester City in advance this month, ran onto Jordi Alba's chipped ball over the top and laid the ball lower back for De Jong to finish from close variety
