However, earlier this week, it was suggested that United were willing to pay in the region of £64m to secure a deal for the centre-back in the summer.
While much could change during the second half of the campaign, many United supporters would deem the signing as value for money, especially when a portion of the financial outlay could be offset by a sale.
That said, Ole Gunnar Solskjaer would be provided with the opportunity to become more versatile should the 28-year-old make the switch to Old Trafford.
Here, Sports Mole predicts how United could line up if they are able to secure the services of Koulibaly.
While Solskjaer has tended to go with a back four during his 13 months in the United dugout, that could change if he pulls off the acquisition of a player who is regarded as African's best centre-back.
With Lindelof comfortable playing on the right and Maguire having proven in the past that he can feature on the left-hand side of a back three, we think that Solskjaer would prefer to use the trio in the same team.
Given Solskjaer's counter-attacking style, the downside would be that just two players would feature in the middle of the pitch to allow United to play with two wingers.
Although Scott McTominay would be an obvious pick, Bruno Fernandes - should he complete his transfer from Sporting Lisbon this month - may have to take on more defensive responsibility than he would perhaps have liked.
Despite the preference being for Marcus Rashford to be used on the flank and Anthony Martial down the middle, the pair could form a front two, with Fernandes being used as the most advanced of a midfield three.body check tags ::