Gerardo Martino's men suffered a rare home loss to Valencia on Saturday and the visitors will be hoping they can make lightning strike twice on Wednesday
Jagoba Arrasate's men will be well aware of the size of the challenge they face in the first leg of their semi-final on Wednesday, having already been beaten 4-1 by Barca this season in September's La Liga meeting at Camp Nou.
Indeed, Sociedad have not won at the home of the current Liga champions since the 1990-91 season.
And when Sociedad last played in the Copa final 26 years ago, it was Barcelona who denied them a second consecutive crown, prevailing 1-0 at the Santiago Bernabeu.
But, with the semi-final being played over two legs, even a draw in Catalunya would give Arrasate's charges a glimmer of hope.
Inconsistent league form has left the Basque club, who finished fourth in the Spanish top flight last season, seven points adrift of the final Champions League qualifying spot.
It is away from home where Sociedad have really struggled, having taken just 13 of their 36 points this term on the road.
Barca, meanwhile, have won 10 of 11 home league matches, the solitary defeat coming on Saturday against Valencia.
That result, combined with Atletico Madrid's 4-0 hammering of Wednesday's opponents, saw Barca fall three points off the title pace.
The visitors may fear a backlash, with Barca having responded to their previous league defeat by winning the next seven games in all competitions, scoring 28 goals in the process.
And goals have flowed readily for Gerardo Martino's side in the Copa del Rey - 22 in six matches underlining their attacking threat.
Neymar has missed the hosts' last six games with a thigh injury and continues his recovery, while Arrasate may look to the likes of Imanol Agirretxe, Haris Seferovic and Gonzalo Castro Irizabal, who all came off the bench in the loss at Atleti.