Turkey's Altay Bayindir is expected to deputise for Onana at Newcastle in what would be only his sixth appearance of the season and his first Premier League game.
He has not featured since January, having played only in cup games this season.
Since the start of last season Onana has made eight errors leading to goals in all competitions, the most of any keeper playing for a Premier League club.
Amorim defended the 29-year-old after the performance against Lyon, saying he had made more mistakes this season than Onana.
Onana has struggled to live up to his £47m transfer fee since his arrival from Inter Milan in 2023.
The then United manager Erik ten Hag ditched popular first-choice David de Gea, believing Onana was better with the ball at his feet.
However, Onana has made a series of mistakes, with the first goal in Lyon, when he dived to push a routine shot away from goal but inexplicably missed it, a prime example.
Aside from Onana's on-field issues, he has also had to deal with off-field problems.
His wife Melanie Kamayou was mugged as she left a restaurant in Cheshire last month.
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