Brendan Rodgers was critical of the VAR officials after Manchester United's Marcel Sabitzer avoided a red card for a knee-high challenge on Leicester's Wout Faes.
Leicester ultimately lost 3-0 to Erik ten Hag's side in Sunday's Premier League fixture, with Marcus Rashford netting a brace and Jadon Sancho also getting on the scoresheet.
Wout Weghorst also missed a late chance to extend the scoreline, but the victory was already wrapped up by then for the hosts at Old Trafford.
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United have closed the gap to Premier League leaders Arsenal to five points, having played a game more, and they face Barcelona at Old Trafford on Thursday in the Europa League.
But one key talking point from the game was the decision by VAR not to award Sabitzer a red card with the score at 1-0 in the first half.
The Austrian midfielder went in for a challenge side-on and caught the knee of Faes, who also committed to a tackle.
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The Foxes defender was able to finish the game, but Leicester manager Rodgers rued a decision that came when his side were very much still in the game at Old Trafford.
Rodgers criticises decision after Man Utd loss
Speaking on BBC Radio 5 Live, Rodgers said: "I'll take away that we should have been playing against 10 men.
"It was a challenge that, how that's not picked up, as a straight-leg stud to the knee on Wout, how that is not a sending off I will never know.
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"Overall it was a disappointing scoreline for us, but they're in a good run of form here, a good moment."
Sabitzer played 80 minutes for United at Old Trafford, and was replaced by 17-year-old Kobbie Mainoo for the final period of the game.
The midfielder will be in contention for the second leg of his side's Europa League play-off clash against Barca, having missed the first leg through suspension.
Topics: Manchester United, Premier League, Brendan Rodgers, Marcel Sabitzer
Ryan Smart