A difficult night inside a hostile atmosphere was made worse just before the break when Marcao scored a bullet-header after Ryan Babel rolled back the years to win a corner.
In Babel and Bafetimbi Gomis, the home side looked to have the kind of direct thrusts to punish Barca, who were often guilty of giving the ball away in a sloppy first forty minutes or so.
Pedri, however, would soon turn on the style.
The Spanish international capped off a flowing team move excellently by almost taunting the Gala defence, offering feints to shoot and sitting down a number of defenders before rolling into the back of the net and restoring parity.
Where the first goal was one of real quality, Pierre-Emerick Aubameyang’s eventual winner was as instinctive as they come. After Frenkie De Jong had headed across goal following a goalmouth scramble, the 32-year-old continued his good form with a ruthless finish from close range.
It wasn’t always pretty for Xavi Hernandez’s side but a professional job done.