The manner of the 1-0 defeat raises new doubts over the quality and character of key personnel and once more increases the scrutiny on their January transfer plans.
Arguably their Arguably their worst performance of the season has left fresh questions over the direction of this team - and particularly the midfield.
Bruno Fernandes and Casemiro have generally performed well this season, but there was always a feeling that the combination was fragile, and that United had no clear back-up if they started to creak.
Now that narrative is being exposed - and the second half opportunity for Kobbie Mainoo seemed little more than a gesture. One he was unable to make the most of.
United do want a new midfielder, but how do they do it? And when?
The chances of them signing an elite, top-tier midfielder are only considered likely in January if there is a good chance of them reaching the Champions League positions.
But we are now 12 games into the season, and United are 10th in the table.
Fresh information over the past week has suggested that United have begun to look more seriously at Joao Gomes of Wolves because he could become attainable.
He is not a top choice, but he is a candidate from within the Premier League that would be cheaper than the likes of Elliot Anderson, Adam Wharton or Carlos Baleba.
Sources believe Gomes has had his head turned by United’s interest - but will they pull the trigger on a bid?
If United’s season has no genuine direction in the second half of the season, it is somewhat possible that they will delay their recruitment process entirely.
Yet the alarming manner of the latest game will lead to new discussions over their recruitment plans - and how aggressively they go into the market.
Casemiro is almost certain to leave at the end of the season, and Mainoo is expected to request a loan transfer in January.
United may ultimately view these growing pains as part of a broader evolution, but they cannot afford missteps.
If they return to the market this winter, their next midfield signing must be the right one.
