United have a resurgent Luke Shaw and an emerging Brandon Williams fighting for the left-back position, but with Diogo Dalot struggling with injuries and fitness concerns throughout his Old Trafford career, Williams is also the primary alternative at right-back as well.
It means even just one injury to Wan-Bissaka, Shaw or Williams threatens to leave manager Ole Gunnar Solskjaer short of options on either side.
There is also a need for greater depth if Solskjaer is to continue using a back-three system as part of his tactical arsenal. That system requires wing-backs and has already seen Shaw in particularly repurposed as a third centre-back on occasion, which again affects depth.
Given that Wan-Bissaka will be a long-term starter, United’s best bet when looking for another right-sided defender is a young developing player or a more experienced veteran, as opposed to a marquee buy at their peak.
Norwich full-back Max Aarons is a player United were linked with last summer as a possible alternative to Wan-Bissaka, but there might still be a need for the Canaries star at Old Trafford.
At 20, Aarons has his whole career ahead of him and has been an important player for Norwich in both their Championship winning season and in the Premier League.
United were criticised when they were first linked with Aarons because his style of play contrasts to Wan-Bissaka’s and it suggested a lack of coherent recruitment policy. But that could now be seen as an advantage if he is able to offer something different.
Where Wan-Bissaka is arguably already the best one-on-one defender in the Premier League but lacks technique going forward, Aarons has more about him in an attacking sense and perhaps needs to pay more attention to defensive duties when making high runs.
The two could even complement each other in the same team should Wan-Bissaka be deployed as third centre-back and Aarons asked to perform a wing-back role.
Potential price: £20-30m
Everton defender Mason Holgate joined the Toffees from Barnsley in 2015 but is still only 23. That puts him into the long-term category that is proving so important for United’s plans.
Holgate looked like his career might have been heading south when he spent the second half of last season on loan at West Brom in the Championship. Yet, having spent the first couple of months of 2019/20 on the bench, he has now firmly established himself as a starter.
Holgate has spent much of this season at centre-back, although he is versatile enough to play at right-back and has done so in the past. That could help him if United were to switch between a flat back four and a back three, as already alluded to.
The former Barnsley youngster is under long-term contract at Goodison Park until 2025, which will serve to keep his price relatively high should United or anyone else make an approach.
Potential price: £30-40m
Only a knee injury that required surgery scuppered an £11m January move for West Brom teenager Nathan Ferguson to Crystal Palace, where he would likely have replaced Wan-Bissaka.
Ferguson is ultimately expected to become a centre-back, although his first-team football this season has come at both right-back and left-back, highlighting excellent versatility.
The Birmingham-born teenager is highly rated and was a regular starter for West Brom in the Championship this season until encountering his injury problem shortly after Christmas. By that point, he already looked likely to leave the Baggies.
Ferguson’s contract, which is still the maiden professional deal he signed in 2017, is due to expire in the coming months. He has resisted a lucrative offer worth a reported £30,000 per week to stay in favour of leaving as a free agent and testing himself with a bigger club.
United, or indeed any suitor, would still be liable to pay a compensation fee due to his age.
Potential price: Free (plus tribunal compensation)
Another emerging talent on course to be out of contract is 21-year-old Tottenham defender Japhet Tanganga. The England youth international has only been part of the first-team squad since January but already looks to be well-liked by Spurs boss Jose Mourinho.
Rather like Ferguson, Tanganga’s versatility has been an asset in helping establish himself at senior level. Although probably a centre-back in the long-term, his handful of first-team appearances so far have seen him feature all across the backline, including at wing-back.
Also like Ferguson, a free transfer would come with a compensation obligation.
Potential price: Free (plus tribunal compensation)
If United wanted to go down the route of a more experienced and established right-back to serve as back-up and provide competition for Wan-Bissaka, Belgium international Thomas Meunier is on course to become a free agent when his contract at Paris Saint-Germain expires this year.
Due to turn 29 in September, Meunier rose to prominence at Club Brugge in his native Belgium and joined PSG four years ago off the back of an impressive showing at Euro 2016.
He has always been subject to squad rotation in Paris and is therefore used to not playing all the time. As a former winger, he also has quality going forward and the capability of operating as a wing-back, as well as just a conventional full-back.
That could be an asset in a fluid tactical playbook that requires a range of skillsets.
Potential price: Free
Right-back featured in 90min’s list of ‘5 Positions Man Utd Need to Strengthen – Summer 2020’ – click to take a look at the other positions discussed and who the club could sign in each.