Ralf Rangnick appears to be plotting an overhaul in defence after Harry Maguire and Raphael Varane failed to convince him they are the partnership to take Manchester United forwards.
Varane, 28, arrived from Real Madrid last summer for an initial fee of £34million to give United what seemed on paper to be a formidable centre-back alliance.
But this has not translated onto the pitch this season and only Southampton (37) have conceded more Premier League goals than the Red Devils (34) among clubs in the top half of the table.
Maguire, 28, has come under particular scrutiny and there have even been calls to strip him of the captain's armband - amid his tussle for power with Cristiano Ronaldo - in a bid to improve his performances.
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Rangnick has since thrown his weight behind the England international to continue as skipper, but the latest reports suggest he remains unconvinced about his options at centre-back.
Mirror Sport understands Old Trafford chiefs are weighing up a swoop for Antonio Rudiger, whose contract with Chelsea expires this summer.
The German, 28, helped the Blues clinch the Champions League last season and he continues to be a standout performer in his position.
Meanwhile, United are also understood to be monitoring Manuel Akanji, who recently turned down the offer of a new contract at Borussia Dortmund.
The Switzerland international, 26, has less than 18 months remaining on his existing deal and reports from Germany linked him with United earlier in February.
According to a fresh report in Sport Bild, Akanji is unhappy with Dortmund's offer of an extension worth €8million (£6.7m) a season and is holding out for his €10million-per-annum (£8.3m) requirements to be met.
Remarkably, United are said to be willing to go above and beyond these demands by presenting the player with a deal worth €15million (£12.5m) per season.
The North-West giants could have the edge in the race for Akanji as they could offer him the chance to reunite with former teammate Jadon Sancho.
Further, their defensive target is known to have a soft spot for United having grown up supporting them and even declared he would "like to play there one day".
Dortmund are believed to be searching for a replacement and have identified Freiburg's Nico Schlotterbeck as a potential option.
So, with Akanji firmly on the radar and Rudiger the latest defender, the United hierarchy is targeting, it may be all change at the back for the Red Devils by the time the start of the 2022/23 season rolls around.
