Michael Carrick instantly solved one of Manchester United's biggest problems from the Ruben Amorim era by simply playing Luke Shaw and Diogo Dalot in their natural positions. The full-backs have started all nine games under the former Red Devils midfielder, playing their part in the coach's astonishing run of seven victories, one draw and one defeat thus far.And yet despite their recent progress, Shaw and Dalot are the two players that tend to attract the most criticism from both match-going fans and those online. Both have visible flaws which many believe are holding the team back from going to the next level.Midfield will be the club's main area of focus in this summer's transfer market as they face the daunting task of replacing Casemiro while still needing to plug the gap in the squad left by Christian Eriksen, but strengthening at full-back is just as important. So, as director of football Jason Wilcox and head of recruitment Christopher Vivell weigh up whether to sign Elliot Anderson or Adam Wharton for a potential £100 million ($132.5m), they must keep some money in the transfer kitty to boost their defensive options out wide."We talk about priority nothing but midfield, that's all we hear about, but let's get something straight about that full-back position," began United hooligan-turned-podcaster Tony O’Neill on the Webby and O’Neill Show. "One won't work without the other. You bring a couple of gems in midfield and have the same problem going forward with the full-backs."The last few seasons it's been mix and match, anyone will do, that's how it's always been, and United have not sorted that problem out. When it comes to Shaw and Dalot, they’ve run their course." Since Shaw arrived from Southampton aged 19 for £30m ($40m)  - then a record fee for a teenager - United have spent just £150m on full-backs in 12 years. To put that figure into perspective, Manchester City spent £127m on three full-backs in one summer alone in 2017.United have gone for both rising stars such as Aaron Wan-Bissaka - who accounts for a third of their total spend on the position at £50m - and Tyrell Malacia, and experienced heads like Alex Telles and Noussair Mazraoui, suggesting they haven't really known what they wanted. Indeed, United seemed to neglect the full-back position so much that at the start of the 2023-24 season they had to sign Sergio Reguilon on an emergency loan due to twin injuries to Shaw and Malacia.In the last year, they spent a combined £32m on Patrick Dorgu and Diego Leon, although the former has been out injured since January while his best performances for United have come when unleashed on the right or left wing. And yet in 2026 their best options remain Shaw, who joined in 2014, and Dalot, who arrived in 2018. The pair have been at United for a combined 20 years, and many United supporters have been crying out for an upgrade."I just see United fans for a long time now saying 'Get Shaw out, get Dalot out and get somebody new in'," O'Neill added. "But that conversation has gone away and it has to turn back to being the priority. You look at that full-back position, where's the competition behind them? "Whoever’s been put in there has just come and gone. There's not been a priority from the club, from the men in the suits on the full-back position. Shaw and Dalot, as far as I'm concerned, their time has come and it's time to go."Shaw is one of the great survivors of the club's history, having played for every manager in the post-Sir Alex Ferguson era aside from David Moyes. But his attacking quality has waned as his energy levels have declined with age and due to so many injuries, and although he has defended superbly throughout the season, both under Amorim and Carrick, Shaw cannot offer what most people expect from a modern full-back.To Shaw's credit, he has stayed injury-free this season and has remarkably played more minutes than any other player in the squad. And yet his history means there are obvious doubts about his longevity, especially seeing as the last time he played regularly, in 2022-23, he was plagued by injuries for the next two seasons.Shaw will have one more year on his contract at the end of this season, and when his deal runs out he will be about to turn 32. He cannot offer what most people expect from a modern full-back, underlined by the fact that despite playing the most minutes, Shaw has only contributed to one goal all season.Add GOAL.com as a preferred source on Google to see more of our reportingDalot has no such problem with athleticism or availability, and he has improved considerably under Carrick, where he can focus primarily on defending rather than chance creation, as was his remit under Amorim. That burden proved even bigger when he was playing on his weaker left side, which he did so often. Dalot has three assists this season, with only Bruno Fernandes providing more in the United squad, as well as one goal. But he is prone to lapses of concentration and his decision-making in the final third, such as spurning two good chances against Aston Villa or misplacing crosses, is a frequent source of frustration for supporters.Annoyingly for United fans, the club had one of the best young full-backs in Europe on their hands but failed to spot his talent. Alvaro Carreras was overlooked by Erik ten Hag in competitive games and was sent on loan to Granada in August 2023, around the same time they were scrambling around to sign Reguilon. He was subsequently sold to Benfica for just £8m, but one year later joined Real Madrid for £43m, where he has impressed during his debut campaign.In contrast to the midfield options, the market for full-backs is more complicated, while some of the best Premier League players in the position over the last few years did not learn their trade patrolling the flanks.Just look at Arsenal, who have converted Ben White, Riccardo Calafiori and Jurrien Timber to the position from centre-back with great success. Or take Pep Guardiola turning Josko Gvardiol from centre-back to left-back and then back to centre-back, or calling Matheus Nunes "one of the best midfielders in the world" when he played for Sporting CP before concluding that he "wasn't intelligent enough" to play in the middle of the park and was much better suited to playing at right-back. Guardiola has also used Nico O'Reilly in a variety of roles, with the England international switching between left-back, holding midfield and attacking midfield.If United want a traditional overlapping, marauding left-back then they should look to Newcastle's Lewis Hall. His team-mate Tino Livramento, who is being targeted by City, is also a tempting option at right-back, but his injury history should ring alarm bells. The stumbling block for both players is their transfer fees, with Newcastle likely to charge in the region of £80m for either player.If United want a player who has already proven themselves in the Premier League - and the success stories of last summer contrasting with the struggles faced by the likes of Manuel Ugarte, Joshua Zirkzee and Rasmus Hojlund in previous years suggest they should - then they could find value in the market by looking to Pedro Porro in the event that Tottenham get relegated, or Ola Aina if Nottingham Forest go down. Hugo Bueno, almost certain to be relegated with Wolves, is an even lower cost option given he would be available for potentially £20m despite having some of the most impressive underlying stats in the Premier League.There are several enticing options outside of England. Julian Ryerson, for example, has provided 12 assists from 18 starts in the Bundesliga and was a key player in Norway's storming through World Cup qualification. The catch is that he plays at right wing-back, ironically making him better suited to Amorim's system than Carrick's, while at 28 he is slightly over the age profile United favour. Reports that Dortmund would accept a fee of around £35m do still make him an attractive option.Fellow German side Eintracht Frankfurt, who had made a killing selling to English clubs lately, have two full-backs that the top sides are taking a close look at in Nathaniel Brown, who has nine goal contributions in all competitions, and Nnamdi Collins.There is, then, no shortage of exciting choices should United look to boost their options at full-back. It is just a matter of prioritising a position which has been neglected for far too long.