Barcelona arrive in San Sebastian looking to put immediate pressure on front-runners Real Madrid, and also stop David Moyes good start in it's tracks.
By the time the referee's whistle goes to kick off this one, Real Madrid will have already played Valencia at Mestalla, and the Catalans will know whether a win will have brought them to within a point or just kept the status quo as it is.
Let's take a look at three things which might shape the outcome of this one.
Barca's rotten record at the Anoeta
Barcelona haven't won at the Anoeta Stadium since 2007 and their performances at the ground have left much to be desired.
February 2014 was the last time Barca came to town and Alex Song's own goal set La Real on their way to a 3-1 victory. Not even Lionel Messi's equaliser to get them back into the game was enough.
A jaded second-half performance mirrored their previous visit where they also conceded three goals and astonishingly gave up a two-goal lead.
Barca have the players to come away with victory but will the jinx already be playing on their minds?
David Moyes good start
Say what you like about David Moyes, and most people do, but he's done well so far in Spain.
In many respects the Scot should be applauded for his bravery in taking a job that brings him right out of his comfort zone.
The game against Barcelona represents by far his stiffest test to date, and an ability to change the game if it begins to move away from the home side will be crucial.
His players have been effusive in their praise of his methods since his arrival and, as with his time at Everton, staff enjoy giving their all for him.
A positive result here will set Sociedad up nicely for the remainder of the season.
This match will be the 25th of Luis Enrique's Barca reign. It will also represent the 25th time he has shuffled his pack.
It's an astonishing statistic, and one that gives rise to the notion that the manager still doesn't really know his best Blaugrana.
That's a real worry at this stage of the season, and such uncertainty could well play into the home sides hands.
Barca have the players to win the game comfortably, but will Enrique's tinkering undo any good work?