Sociedad moved above Real Madrid atop the La Liga standings after Mikel Oyarzabal's brace helped earn a 4-1 victory over Huesca at the weekend, while Napoli beat Benevento to sit second in Serie A.
An injury-time strike from substitute Jon Bautista gave the Liga leaders Real a dramatic 1-0 victory at Croatian side Rijeka on the opening day of their European campaign.
Napoli, meanwhile, were shocked by AZ Alkmaar, losing by the same score at San Paolo - despite having 73% possession - to end the Partenopei's six-match home winning run in Europa League group stage matches.
Imanol Alguacil's Sociedad side will be looking to make a serious impression in European competition this season as they also seek to push for a top four place, having ended the 2019-20 campaign in sixth.
That was enough to secure La Real a return to European football after a two-season absence. They also reached the final of the Copa del Rey, against Basque rivals Athletic Club, but that fixture has been postponed indefinitely.
This season has started in a similar vein - including in Europe - as they seem to have effortlessly overcome the departure of chief creator Martin Odegaard. The signing of Manchester City legend David Silva, of course, helped significantly in that regard.
Napoli continued their ascendant trajectory on Sunday, as both Insigne brothers - the Neapolitan club's captain Lorenzo and Benevento striker Roberto - found the net in the Campania derby, with Andrea Petagna later replacing Dries Mertens to score the winner. It was closer run than many expected beforehand, but Gennaro Gattuso's side still sealed the three points.
Now their attention reverts to continental matters. After four successive seasons in the Champions League, Napoli returned to the Europa League group stage, courtesy of winning the Coppa Italia via a shoot-out victory against Juventus, and are surely aiming to win it.
The Italian heavyweights have never failed to qualify from their section at this level, winning all six matches last time out in 2015-16, when they also set the current record for the most goals scored in a Europa League group (22).
However, there have been just two wins for Napoli in their last ten European away fixtures, which may strike a note of caution in their camp before this tough assignment in Northern Spain.
They travel to the Anoeta, then, with recent precedent against them and facing a stern test of their ever-rising confidence. It promises to be quite a clash, even one befitting a final.
Real Sociedad Europa League form: W
Real Sociedad form (all competitions): WLWWWW
Napoli Europa League form: L
Napoli form (all competitions): WWLWLW
There are doubts over the availability of former Manchester United winger Adnan Januzaj, forwards Ander Barrenetxea and Martin Merquelanz, right-back Joseba Zaldua and highly-rated midfielder Igor Zubeldia.
Oyarzabal and exciting Sweden forward Alexander Isak should lead the attack for Imanol Alguacil's side.
Meanwhile, Napoli are in the rare and fortunate position of having no serious injury concerns, so manager Gennaro Gattuso is expected to have a fully-fit squad at his disposal.
Real Sociedad possible starting lineup:
Remiro; Gorosabel, Elustondo, Le Normand, Monreal; Zubimendi, Silva, Merino; Portu, Isak, Oyarzabal
Napoli possible starting lineup:
Meret; Di Lorenzo, Manolas, Koulibaly, Hysaj; Ruiz, Lobotka; Politano, Mertens, Lozano; Osimhen
We say: Real Sociedad 2-2 Napoli
Both sides are on the up domestically, but are already separated by three points in Europa League Group F.
There is little to separate them in terms of quality, even if the visitors can boast more recent European experience - most of which was at a higher level.
Napoli's explosive attack - plus their need to get off the mark - can inspire them to take at least a point home from this enticing encounter.