How could United's injury-plagued defence shape up vs. Celta Vigo?

With Manchester United running out of time to crash the Premier League's top-four party, Jose Mourinho's only route to Champions League football next season could be via victory at the Swedish national stadium in Stockholm on May 24.

For some, the Europa League is a booby prize recognising an ultimately unsuccessful push for England's best quartet, and United certainly faced a legion of minnows from unheralded and weather-ravaged corners of the continent en route to the semi-finals. But, after taking on the likes of Zorya Luhansk and FC Rostov, the Stretford outfit will pit itself against Celta Vigo in Thursday's semi-final first leg with a defence depleted by injuries.

Luke Shaw suffered foot ligament damage in Sunday's 1-1 home draw with Swansea City, according to BBC Sport, and joins Phil Jones, Chris Smalling, Eric Bailly, Marcos Rojo, and Timothy Fosu-Mensah in the treatment room. That means there are no senior centre-halves at Mourinho's disposal, and the auxiliary options are lacking, since Paul Pogba - someone Mourinho talked up as a potentially "phenomenal" defender last October - is also nursing an ailment.

So, facing an energetic Celta Vigo side that's been resting its key players lately, how will the Portuguese gaffer tend to the drained defensive resources at United?

Back four

Mourinho could revert to type with a back four and two defensively minded midfielders - the foundations of the 4-2-3-1 he stubbornly deployed week after week earlier in the season.

This means both lines would feature personnel seasoned by the rigours of senior action, with Michael Carrick filling in at centre-half, just as he did in a 5-1 win over FC Midtjylland in last term's competition.

Matteo Darmian is another option to fill in at centre-half, but Daley Blind would be the more natural choice there while the Italian, a right-back by trade, continues to patrol the left.

Back three

For the usually pragmatic Mourinho, this would be a decision out of left field, but it may make tactical sense.

In Galicia, the home side will look to be on the ascendancy and should be fresh after various first-team regulars sat out the formality of finishing a mid-table standing in La Liga. For this, a solid back three that can easily mold into a five may be the most sensible choice when attempting to stymie a high press and fluid frontline.

To field this shape, Mourinho would likely have to dip into reserve. Axel Tuanzebe, who served as Under-18 captain as a first-year scholar, is a promising talent, but the 19-year-old only has 22 first-team minutes to his name, all as a substitute in January's 4-0 FA Cup stuffing of Wigan Athletic. Outside of that, Marouane Fellaini could make amends for his Manchester derby red card by dropping back into a makeshift trio, or a fit Pogba could deputise.