The Cameroonian goalkeeper has faced several errors since joining the Old Trafford giants, with former teammate Nemanja Matic calling the African "one of the worst goalkeepers in the club's history."
However, the Dane, has come to Onana's defense, highlighting the "mental toughness" he has demonstrated.
"It’s been a difficult year, it’s been a difficult year for everyone, so singling out anyone, I think that would be very, very wrong. Just look where Manchester United are in the Premier League,” Schmeichel told talkSPORT.
"The players are not having the greatest time. I try to explain this to people, why is it different playing for Manchester United as opposed to any other club?
"I showed this to my wife the other day. We have a broadsheet newspaper in Denmark that doesn’t have a sports section, but they still carry Manchester United’s results and not just a little line but in an article.”