Real Sociedad have simply capitulated in recent weeks and are slowly slipping away from the title-chasing pack amid an abysmal run of form.
The Whites and Blues can only boast a mere one win from their last 12 in all competitions - a 1-0 triumph over Athletic Bilbao on New Year's Eve - and Sevilla were indebted to Youssef En-Nesyri as his hat-trick condemned Sociedad to their fifth league defeat of the campaign at the weekend.
Alguacil's men were the only team in the top six to lose at the weekend and now find themselves eight points behind leaders Atletico Madrid having played four games more, but they now have a two-week break from league action as cup competitions take centre stage.
This is only the second time that the Supercopa de Espana has involved four teams, and Sociedad won the inaugural edition of the tournament in 1982 - defeating Real Madrid 4-1 on aggregate over a two-legged final.
Sociedad and Barca will be battling for the chance to meet either Real Madrid or Athletic in Sunday's final, and while Alguacil's side may not feel at all confident about claiming a rare win here, they can look forward to a Copa del Rey clash with third-tier Cordoba next week.
With wantaway talisman Lionel Messi now firing on all cylinders, Barcelona are flying high and needed no second invitation to cruise past an inconsistent Granada at the weekend.
Messi struck twice while Antoine Griezmann netted a brace of his own to stretch La Blaugrana's unbeaten streak to eight matches, with six of those games ending in wins for Barcelona - four of which have come away from home.
Ronald Koeman's side have travelled to unfamiliar territory and come out on top three times in a row in 2021, and Barca now find themselves third in the La Liga table - four points behind Atletico, who have played three fewer matches.
La Blaugrana's 2019-20 Supercopa de Espana attempt ended at the first hurdle as Atletico knocked them out in the semi-finals in Saudi Arabia, but they have won this competition a record 13 times down the years as well as collecting 10 runner-up medals.
Real Sociedad form: LLLWDL
Barcelona form: DWDWWW
However, there is optimism over the fitness of veteran defender Nacho Monreal, who should start at left-back following reports that he has now returned to full training.
Alexander Isak found the back of the net at the weekend but could find his spot up top under threat from Willian Jose, while Asier Illarramendi and Robin Le Normand could both be reintroduced to the first XI.
It is still too soon for Philippe Coutinho, Gerard Pique, Sergi Roberto and Ansu Fati to return to action, but Koeman is expected to stick with the majority of the side that dispatched Granada with ease on Saturday.
Messi boasts 25 goal contributions (16 goals, nine assists) in all competitions against Sociedad and is set to be supported by Griezmann and Ousmane Dembele on the flanks.
Real Sociedad possible starting lineup:
Remiro; Gorosabel, Le Normand, Zubeldia, Monreal; Illarramendi, Merino, Guevara; Porto, Jose, Oyarzabal
Barcelona possible starting lineup:
Ter Stegen; Dest, Araujo, Lenglet, Alba; Busquets, De Jong, Pedri; Dembele, Messi, Griezmann
We say: Real Sociedad 1-2 Barcelona
Real Sociedad still carry plenty of threat going forward despite their underwhelming form, and the prospect of silverware should act as an incentive for Alguacil's men to pull off a shock result. However, we cannot look past Barcelona in their current form and expect La Blaugrana to advance to their 24th Supercopa de Espana final this week.