This competition represents Man United's only chance of getting into the Champions League, considering they are in the bottom half of the Premier League table.
It would also give Ruben Amorim the chance to win a trophy, with the FA Cup no longer an option after Fulham defeated the Red Devils on penalties at the weekend.
It was the latest setback in a shambolic season for United, but the Europa League is still an opportunity.
Under the new format, no Champions League sides have dropped into the competition, meaning the Red Devils are still one of the strongest sides remaining.
However, this won't be an easy task after Sociedad thrashed FC Midtjylland in the last round, while they are still in the hunt for European places in LaLiga.
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Real Sociedad vs Man United: Striker woe
It would be hard to pick out one particular issue with Manchester United, but an obvious one is up front.
The Red Devils have two senior strikers to pick from, in Joshua Zirkzee and Rasmus Hojlund, but both are massively struggling.
Hojlund hasn't scored a goal in 18 matches, though he has five in the Europa League, and looks short on confidence.
Meanwhile, Zirkzee has five goals all year across all competitions and just missed the decisive spot kick against Fulham in the FA Cup.
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Both are still young and have time to turn it around, but as it stands, neither is the striker Man United need.
Real Sociedad have won just one of their previous six European encounters against Manchester United (D2 L3), with that win coming in the group stage of this competition at Old Trafford in September 2022. They won that game 1-0 courtesy of a Brais Méndez penalty, which remains their only goal against them.
Real Sociedad have never beaten an English side on home soil in Europe (D1 L3), failing to score in each of the last three matches (all against Man Utd). They are, however, one of six sides to score in 100% of their UEFA Europa League games this season (10/10), with Man Utd also doing so (8/8).
Real Sociedad vs Man United: Team news
The hosts are sweating over the fitness of key man Martin Zubimendi.
The Spanish international came off at half time during Sociedad's 4-0 defeat to Barcelona.
For United, there are lots of injury problems.
Amad Diallo has been ruled out until the end of the season, while there appears no chance of Mason Mount or Luke Shaw appearing any time soon.
Lisandro Martinez is also out for the rest of the year after suffering an ACL injury.
Kobbie Mainoo, Altay Bayindir and Jonny Evans all remain on the sidelines.
However, Toby Collyer could be in contention, but Chido Obi-Martin is ineligible.
Man Utd have lost just one of their last eight away games against Spanish opposition in Europe (W5 D2), however that defeat did come in their most recent such encounter, losing 3-0 at Sevilla in the second leg of the 2022-23 UEFA Europa League quarter final.
Real Sociedad have failed to progress from any of their previous four last 16 ties in major European competition, since knocking German side 1. FC Köln out of the UEFA Cup back in 1988-89.
Man Utd are averaging 18.8 shots per game in the UEFA Europa League this season, the most of any side still in the competition and their best ratio in a European season on record (since 2003-04). They also have the highest average sequence time (12.9 seconds), passes per sequence (4.5) and possession (61.2%).
Real Sociedad vs Man United: What has been said?
Man United legend Wayne Rooney wishes Danny Welbeck was still at Old Trafford.
Speaking to the BBC, he said: "Danny, he's great to play alongside and if I'm being completely honest, I'd would probably still like to see him here playing for Manchester United.
"He scored goals throughout his career, had injuries in early part of his career, but seems to have got over them and he's having a fantastic season."
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Real Sociedad vs Man United: talkSPORT coverage
The first leg of this Europa League last-16 clash is set to take place on Thursday, March 6.
Kick-off at the Reale Arena is schedueld for 5:45pm UK time.
talkSPORT will have live coverage of the match, with Andy Goldstein serving as your host.
Commentary will then come from Jim Proudfoot and former Tottenham striker Darren Bent.
talkSPORT.com will also have updates throughout and all of the reaction after.
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