Real Sociedad began the league phase with a draw against Nice, while Anderlecht took maximum points from their home meeting with Ferencvaros.
Match preview
Real Sociedad are preparing to play their first European home match since losing 2-1 in the second leg of March's Champions League last-16 tie.
La Real have had to settle for a Europa League appearance this time around following their sixth-place finish in La Liga last season.
Imanol Alguacil's side began their European campaign with a battling display in the South of France last week, with Ander Barrenetxea scoring an 18th-minute opener in a 1-1 draw against Nice.
While Real Sociedad would have been content with an away point, the result did extend their winless run to six matches in all competitions.
Fortunately for La Real, they ended their wait for a precious victory in Saturday's home league game against Valencia, with Take Kubo finding the net before Orri Oskarsson came off the bench to register a late brace and wrap up a commanding 3-0 victory.
After claiming their first home win of the season, the Basque club will be targeting another strong home performance in their first meeting with Anderlecht in UEFA competition.
Anderlecht are competing in the Europa League main draw for the first time since 2018-19 after they qualified for the playoff round via last season's third-place finish.
The Purple & White secured their spot in the league phase with a 2-0 aggregate victory over Belarusian champions Dinamo Minsk.
The Belgians are now hoping to enjoy a successful league phase as they look to progress to the Europa League knockout rounds for the first time since reaching the quarter-finals in 2016-17.
Anderlecht's produced a positive result in their first match of the main draw, with Yari Verschaeren and Kasper Dolberg scoring a goal apiece to fire their side to a 2-1 home win over Ferencvaros.
That result has proven to be David Hubert's only win in his three games as interim boss, having seen his first two league matches finish all square.
As a result, Anderlecht have won just one of their previous six competitive matches, but as they turn their focus to a trip to Spain, they can take confidence from the fact they have avoided defeat in all five of their away games this season.
Real Sociedad Europa League form:
D
Real Sociedad form (all competitions):
D
L
L
D
D
W
Anderlecht Europa League form:
W
W
W
Anderlecht form (all competitions):
D
D
L
D
W
D
Team News
Real Sociedad remain without defender Hamari Traore and midfielder Arsen Zakharyan, who are sidelined with knee and ankle injuries respectively.
Alvaro Odriozola and Sheraldo Becker are expected to return to the matchday squad after they were forced to miss the win over Valencia due to physical issues.
Alguacil is likely to make changes from the weekend, with Odriozola, Jon Pacheco, Aihen Munoz, Brais Mendez and Benat Turrientes all hoping to start on Wednesday.
Oskarsson may also be considered for a starting spot after he came off the bench to score a brace at the weekend.
As for the visitors, they are unable to call upon the services of Ludwig Augustinsson, Thorgan Hazard, Marco Kana and Jan Vertonghen.
Midfielder Nilson Angulo is set to serve a one-match suspension after being sent off for two bookable offences against Ferencvaros.
Anders Dreyer returned from a three-game injury absence to play over an hour in Saturday's away clash with Dender, and he is poised to retain his place in the front three for Thursday's trip to Spain.
Real Sociedad possible starting lineup:
Remiro; Odriozola, Zubeldia, Pacheco, Munoz; Kubo, Mendez, Zubimendi, Turrientes, Barrenetxea; Oskarsson
Anderlecht possible starting lineup:
Coosemans; Sardella, Simic, Zanka, N'Diaye; Verschaeren, Dendoncker, Stroeykens; Edozie, Dreyer, Dolberg