New Red Devils head coach Ruben Amorim is widely expected to implement a 3-4-3 system at Old Trafford, having had huge success with that formation at Sporting Lisbon.
Man United have again had left-back issues this season due to the absences of Luke Shaw and Tyrell Malacia, but the pair are both now back to fitness at a crucial stage of the campaign.
Shaw has returned to training after recovering from a calf issue, while Malacia played 45 minutes for Man United Under-21s in the EFL Trophy against Huddersfield Town last week - his first appearance since May 2023.
There remain concerns over Shaw's long-term fitness, though, with the Englishman struggling with muscular injuries in recent years, while Malacia recently detailed the seriousness of his knee injury.
Man United 'planning to sign a new left-back'
According to transfer expert Fabrizio Romano, a new left-back is seen as a priority for Amorim, with the club said to have a shortlist of at least three players.
Romano claims that a January deal is possible, although it is most likely that the 20-time English champions will wait until next summer before addressing the issue in their squad.
Bayern Munich's Alphonso Davies is believed to be the club's 'dream target' for the left-sided wing-back role, with the Canada international's contract at Allianz Arena due to expire next summer.
Real Madrid are believed to be firmly at the head of the queue for Davies, but it has been claimed that Man United are prepared to offer him a more lucrative contract to move to Old Trafford at the end of the campaign.
Which other players are options for Man United?
Bournemouth's Milos Kerkez is said to be admired by Man United, with the Hungary international also believed to be on the club's shortlist.
The 21-year-old impressed for Bournemouth last season after his arrival from AZ Alkmaar, and he has again been an important player for the Cherries this season, making 11 appearances, contributing two assists in the process.
Wolverhampton Wanderers' Rayan Ait-Nouri is another player allegedly being tracked by Man United, with the 23-year-old in excellent form this season, scoring three goals and registering two assists in 11 Premier League appearances.
Ait-Nouri's contract at Molineux is due to expire in June 2026, although Wolves can activate an additional 12 months, placing the club in a strong position when it comes to the Algeria international's future.