The Sky Sports Premier League channel was showing The Football Show programme, which had just come to an end before Mills and Peter Graves’ brief chat on-camera.
Appearing to be under the impression they were no longer live, Graves thanked his two guests – Sol Bamba being the other – for the chat on the Premier League club.
Mills then responded with: “Basically, United are just s**t,” prompting laughter from both his colleagues.
Though he initially continued to speak, following up with “But they are!”, Sky quickly cut away from the broadcast a few seconds later, before going to the ad break they were presumably supposed to be on originally – and which Sky Sports News, also broadcasting the same show, had done so.
Several viewers posted footage of the exchange onto social media within minutes, prompting more laughter from football fans in agreement with Mills’ damning, if rather blunt, assessment of the team.
United have been widely criticised since they were beaten 5-0 by their rivals on Sunday, leading to much talk over whether Ole Gunnar Solskjaer may lose his job as manager.
However, the Independent has learned he is likely to remain in position for the weekend Premier League clash against Tottenham.