As de Godenzonen put one foot in the final on May 24, following a handsome 4-1 win versus Bruno Génésio's men at the Amsterdam Arena on Wednesday evening, The Red Devils are odds-on to join them in the Swedish capital at the end of the month. However Celta de Vigo cannot be overlooked.
Whilst it is true that Celta are on a run of three successive La Liga defeats at home to Real Betis, Athletic Bilbao and away to Sevilla - sitting in mid-table no doubt - Celestes have a point to prove to their doubters, not least in personnel.
Celta, led by the growing reputation of former Argentine international Eduardo Berizzo have blazed a trail which up to this stage in the competition, few can turn a blind eye to.
Their route to the last four has been rubber stamped with impressive away victories in both the group stages and the knockout ones.
Not least a hugely impressive 2-1 aggregate victory over Shakhtar Donetsk in the last 32, including a 2-0 win at Metalist Stadium. A similarly resolute display away to FC Krasnodar in the following round followed.
It is worth noting also, that Berizzo's side beat Real Madrid in the Bernabeu in the Copa del Rey back in January.
If their home performances have been less spectacular, Jose Mourinho must be wary of Celta Vigo's road form, particularly with reference to United's struggles at Old Trafford this term.
Aspas keen to make statement
Whilst a defensive unit able of frustrating the opposition, it is the attacking threat of Celta that has unerringly guided them to the semi-finals. Far from household names also, there will more than one or two keen to write wrongs.
Not least Celta's top scorer this campaign, Iago Aspas. The Spaniard, who made a less earth-shattering impact when he made the £9m switch to Liverpool in 2013.
Failing to score in 14 appearances for The Reds, Aspas' final meaningful contribution for Brendan Rodgers side was punctuated by his now notoriously poor corner kick in stoppage time versus Chelsea at Anfield in April 2014, which led to The Blues' counter attack second decisive goal as Liverpool's title charge collapsed spectacularly.
Since the 29 year-old's nightmare that has led to many a meme on social media, Aspas has returned to his native Celta and become not only the striker that garnered his initial move to the Premier League, but has now matured and become a marksman to be feared, scoring 24 goals in all competitions this term, with a razor-like turn of pace.
Celestial fire power
It is not only Aspas that Celta boast. Former Manchester City striker John Guidetti was perhaps more known for his goalscoring for both Celtic and Ajax, but is no less a scoring threat for a depleted Manchester United defence with four goals this tournament.
Ugandan-born Pione Sisto has become real physical presence for Eduardo Berizzo in midfield and has now also began to add goals to his game and scored home and away versus Genk in the last round.
If nothing more than sheer pace, speedster Claudio Beauvue will provide a test down the United flanks. Whilst not a renowned goalscorer, the former Lyon winger will be menace in the channels.
Then of course there is that extra spice added by former Red Devil himself Giuseppe Rossi. Likely to be no more than a substitute to bring on later in the game, the on-loan Italian still has a turn of pace and an eye for goal in his thirties.