Manchester United could be about to do what Man City did in the transfer market

Teden Mengi has been compared to Matthijs de Ligt by Ole Gunnar Solskjaer and Man United need new blood at centre half.

It was in that other ramshackle pre-season of 2018 that Luke Shaw was fat-shamed and subjected to online bullying yet began the campaign better than any of his teammates.

On Friday, the United Twitter account published a picture of Shaw in training looking lithe. For those who watched the rerun of Saturday's friendly at Aston Villa, Shaw was an energetic presence down the left and many of United's best openings stemmed from his side. So did Villa's goal, though Harry Maguire was most blameworthy.

United need their full-backs to be more proactive and penetrative but Shaw was already doing that until he succumbed to injury in July. United were not as accomplished without him in their final matches and Jose Mourinho, once Shaw's biggest detractor, is believed to have marvelled at the left-back's form. In spite of their past, Mourinho views Shaw as a 'good kid'

The 'kid' is now 25 and a veteran of six years at United. Should United succeed in shifting Chris Smalling and the seldom seen Phil Jones before October 5, Shaw would be their fourth-longest servant at first-team level.

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There is still scrutiny over his role. United are considering left-backs, among them Sergio Reguilon and Vitaliy Mykolenko, having monitored Ben Chilwell last year. Left-back is not a priority in this window and the expectation is one will not arrive before it closes in three weeks.

United have phased out elderly full-backs in Antonio Valencia and Ashley Young over the last 18 months yet there could be a proper purge at centre-back. Smalling and Marcos Rojo are training in their own 'outgoings' bubble at Carrington amid the possibility of transfers and Jones started twice in the Premier League last term: he was hooked at half-time in one and United lost the other.

Mourinho envied Pep Guardiola's license to overhaul an entire department in a single window in 2017 when three of Manchester City's full-backs - Pablo Zabaleta, Bacary Sagna and Gael Clichy - were released and the other, Aleksandar Kolarov, was sold. City recruited Benjamin Mendy, Kyle Walker and Danilo for a combined £128.5million and senior figures at United maintain the Walker deal distorted the market for defenders.

United could have released Smalling, Jones and Rojo by now yet all three received new contracts within a 12-month period. Rojo's old deal expired in 2019 and the terms of Smalling's and Jones's previous paperwork included one-year extensions until 2020.

The sale of Smalling to Roma could bank United the best part of £20m for a 30-year-old whose passing was derided by Mourinho on the eve of a European final. Jones has started in eight league games since agreeing a four-and-a-half year deal in February 2019 and Rojo, who posed in the Carrington press room with pen and paper two-and-a-half years ago, has made five starts since.

It still seems unfeasible that United, the shyest of market stall sellers, could flog three central defenders who have been at the club for a combined 25 years, in under a month. Smalling and Rojo were intrepid enough to embark on loans whereas Jones, a Lancashire resident all his life, is nestled in his comfort zone.

Ole Gunnar Solskjaer rhapsodized about Teden Mengi, the 18-year-old defender, twice last week and likened him to Matthijs de Ligt at the same age. Unless it is another case of Solskjaer misdirection, that does not sound like a manager preparing to give Dayot Upamecano a tour of Carrington.

Mengi enjoyed more first-team exposure at Villa Park and a year after skippering the Under-18s to the FA Youth Cup semi-finals as a 17-year-old he has been promised the armband at Under-23 level. He is likely to switch between first and reserve team dressing rooms until his name is fitted above one of the lockers in the main hub but travelled to Villa in July and watched on from the stands. He has since debuted against LASK and received a more flattering squad number.

Plans for a new centre half are due to be parked until next year with such a bloated department already on the books. United have to cut away the fat before they can flesh it out again and Eric Bailly is on trial this season. The 26-year-old has entered the final two years of his contract and started 20 league games in the last three seasons.

Axel Tuanzebe is due to be eased back into the fold and sources close to the academy graduate say he is feeling 'brand new' after a foot operation. When fit, Tuanzebe is the most dependable defender who could break up the pedestrian axis of Maguire and Victor Lindelof.

Elite squads need five centre halves, minimum, for this most gruelling of seasons, with one to emerge from the academy. City had a porous quartet of Aymeric Laporte, John Stones, Nicolas Otamendi and the auxiliary Fernandino, with Eric Garcia breaking through, but had counted on signing Maguire. They have already added Nathan Ake and are pursuing Kalidou Koulibaly.

On Sir Alex Ferguson's squad sheet 16 years ago, players were split into categories of 'squad', 'excess', 'youth potential' and 'transfer targets/possibilities'. Maguire, Lindelof, Bailly and Tuanzebe are 'squad', Smalling, Rojo and Jones the 'excess' and Mengi 'youth potential'. One of United's defensive 'excess' could cling on but Mengi might already be ahead of them.

Jettisoning two this summer and two next summer would free up room for Upamecano or an alternative in 2021.