Speaking in an interview after United's 2-2 Europa League draw with Lyon, the 15-time trophy winner didn't mince words.
"You never feel safe," Schmeichel said of Onana's performances. "Even at 2-1 up, you're always fearing the other team will claw their way back."
Onana's errors in the Lyon match drew particular scrutiny. The first goal, Schmeichel noted, came from a shot where "he should have dealt with it" despite players running across his line of sight.
The second? "A hard shot, straight at him," Schmeichel said, shaking his head. "He should have kept it."
The spotlight on Onana intensified amid a separate spat with former United midfielder Nemanja Matic, whose comments about his old club stirred debate.
Schmeichel, empathetic, suggested Matic's response was heat-of-the-moment. "He probably felt insulted," Schmeichel said. "As a former player who did well for United, he still cares about the club. Sometimes, with all the media demands, you say something that comes out differently."
Yet Schmeichel was clear that Onana's woes aren't the sole issue. "Is he the problem? The defence? The midfield?" he asked. "Ruben Amorim has so many issues to sort out.
Pointing at one player feels unfair." Still, he admitted, "It's not great to watch."
Manchester United's official channels have remained tight-lipped on Onana specifically, but Amorim, in a recent post on X, praised the team's resilience in Europe: "A point away at Lyon keeps us fighting. We build from here."
Meanwhile, Onana's own X post after the match struck a defiant tone: "Head up, we keep pushing forward."
For United fans, Schmeichel's words hit home. A 2-2 draw away isn't disastrous, and their Europa League campaign remains solid at Old Trafford. But with Onana's errors mounting, Amorim faces a critical summer to steady a ship that, as Schmeichel put it, never feels secure.