It is fourth vs fifth in La Liga, with both clubs desperate to gatecrash the Champions League spots this season.
Of the two, Real Sociedad are two points better off right now, despite the fact they were beaten 1-0 by Valladolid last weekend.
Before this, Imanol Alguacil’s team had won five on the bounce, so start the weekend in the top four.
Real Betis meanwhile also lost last weekend, going down 2-1 to Atlético Madrid.
Los Verdiblancos have only won one of their last five, despite winning five of their first six.
Both clubs were in Europa League action on Thursday, both in strong positions to reach the round of 16.
Betis have rubber stamped top spot in Group C, beating Ludogorets in Razgrad this week.
Real Sociedad meantime just need to avoid a 2+ goal defeat at home to Manchester United to finish first, after a 2-0 win over Omonia in Nisocia.
Before matchday six, who will win this key La Liga clash at Reale Arena?