Erik ten Hag and Ruud van Nistelrooy looked to be involved in a heated discussion in the 0-0 draw against Aston Villa, prompting reaction from fans.
United travelled to Villa Park hoping to put an end to their winless run but the streak was extended to five games after a dire game in the West Midlands.
The Red Devils, who had Harry Maguire limp off at half-time and were fortunate to not have Marcus Rashford sent off, are currently 14th in the Premier League after the result.
The poor performance did not do anything to alleviate any pressure on Ten Hag, who had the full INEOS and United hierarchy watching on.
And supporters picked up on a prickly moment between Ten Hag and Van Nistelrooy.
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Sky Sports cameras captured the Dutch pair in dialogue on the bench, with both looking less than happy going off their body language and animated gestures.
Though it was difficult to lip read what was being said, it certainly didn't seem as though there were in agreement.
One wrote: "Erik ten Hag and Ruud van Nistelrooy seem to disagree on the bench."
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A second laughed: "Ruud Van Nistelrooy and Erik ten Hag fighting on the bench like Harry Potter and Voldemort."
A third added: "An animated conversation between Erik ten Hag and Ruud van Nistelrooy…
Another user speculated: "You just know Ruud wasn’t happy with erik ten hag subbing Marcus Rashford out."
A fifth commented: "Can someone help with the lip read please? Erik Ten Hag and Ruud Van Nistelrooy having a heated argument."
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Van Nistelrooy, who scored 150 goals for United, returned to Old Trafford in the summer to become Ten Hag's assistant.
He has been heavily linked to take over an interim basis if United's top brass do decide to pull the trigger on Ten Hag.
United are experiencing their worst ever start to the Premier League season after taking just eight points from seven games.
Topics: Erik Ten Hag, Ruud Van Nistelrooy, Manchester United, Fan Reactions
Josh Lawless