Onana has faced a lot of criticism since arriving at United but Schmeichel called him a hero for his role in the win.
United were in desperate need of three points against Copenhagen but almost threw the win away after Scott McTominay conceded an injury-time penalty.
But Onana dived to his left to keep out Jordan Larsson’s spot-kick and won the match for the Red Devils.
Schmeichel, watching on from the touchline, roared with delighted and pumped his fists alongside fellow club icons Rio Ferdinand and Paul Scholes.
The great Dane was a lot more animated than his TNT Sport colleagues and fans loved seeing his passion on show.
One fan reacted saying: “Go on Peter!”
Another added: “Who’s cutting onions in here??”
A third wrote: “What a great celebration 🎉 from the legend.”
And another commented: “Look at the reaction from Schmeichel! Brilliant to see! 👏”
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Schmeichel spoke to Onana following the game and suggested the goalkeeper was too modest after he claimed Maguire was the hero, not him.
Onana said: “For me, for the club, for the team it was important. It was an important victory for us, difficult game against a very good team. The most important thing today was to win, so I’m happy for the victory, but but we have to move on.”
When Schmeichel described Onana as a hero, the Cameroonian replied: “I don’t think so. I think the hero tonight is Harry, he scored the goal, he gave us the victory today.”