Man United were linked with numerous centre backs during the summer with a suitable partner to Harry Maguire yet to be found at the club.
Lindelof has played the most games alongside the English man but he has come in for countless criticisms.
Also, the club fear for Lindelof's long term fitness while Axel Tuanzebe and Eric Bailly are usually one good performance away from a long term injury.
Due to those factors, Man Utd are monitoring the futures of two French centre backs with a view to luring them to Old Trafford in the summer of 2021.
Dayot Upamecano has a 41 million pounds release clause which would become active on 1st July 2021.
Man utd were linked during the summer but the French man extended his contract with the Red Bull club. United nearly signed then 16-year old Upamecano in 2015 and wouldn't like to miss a second opportunity.
Nothing can stop the deal if United pay the buyout clause.
Raphael Varane has 18 months left on his current Real Madrid contract.
He has a release clause in excess of €500 million euros but that's a very unrealistic figure.
He could even be sold for less than 10% of that given that when summer 2021 transfer window comes around, only one year will be left.
Madrid won't like to lose him for free so if he doesn't extend by then, United are said to be monitoring developments with a view to making a bid.
It's all set to be a very interesting next summer less than two months out of the previous one.