The Red Devils’ loss would not be on the Frenchman himself, however, but a devastating domino effect which could change the path for one of Europe’s other top youngsters.
United are sure to hunt a marquee striker over the next 12 months, with Cristiano Ronaldo days away from his 37th birthday and Edinson Cavani not far behind.
Elsewhere in their ranks, the likes of Marcus Rashford and Mason Greenwood have got plenty to prove before they are likely to be trusted to lead the line.
A club of United’s stature and riches are sure to throw their hat into the ring when it comes to the top names on the continent.
Mbappe certainly falls into that category as a name towards the very top of that list, but United may be more concerned with another – Erling Haaland.
When it comes to those two ambitions options, Mbappe’s future has seemed destined for Real Madrid since last summer, when Los Blancos saw a mammoth £172million to secure his services rejected.
In a surprising turn of events, however, The Telegraph claim that the 23-year-old is in talks to extend his stay at the Parc des Princes.
Madrid seem intent on bringing in a huge name to satisfy their fans over the next few months, and if Mbappe becomes unavailable, there would not be too many eyebrows raised if they turned their attention to Haaland.
Real held a meeting with the Norwegian’s entourage in April of last year, although links recently went quiet with plenty assuming that the Spanish outfit would splash out on Mbappe instead.
Given the pulling power at the Bernabeu, a swoop for Haaland could effectively take him off the market for all other potential suitors.
Of which there are many, not least United who would benefit from signing the 21-year-old not just in terms of the ruthless goal-scoring ability he brings, but because it would stop him potentially going to a Premier League rival.
Manchester City have also been heavily linked with the Borussia Dortmund star, who has scored 21 goals in 18 games across all competitions this campaign.
The Sky Blues have operated without a striker this season, and despite a handful of top-class options in the shop window this January, they appear to be saving themselves for a summer swoop.
If United, and indeed City are to avoid being on the wrong end of a transfer domino effect, they may have to act quickly after Haaland’s statement on Friday evening.
In predictable fashion, the 6ft 4in marksman helped himself to two goals on the way to a resounding 5-1 Dortmund victory.
“Borussia Dortmund are now pushing me to make a decision about things, but I just want to play football,” he said.
“That probably means that I will soon have to get things started. I never spoke until now to respect the club.”