Onana has faced heavy criticism for his performance against Lyon in the Europa League on Thursday night, with the Cameroonian making two high-profile mistakes in the 2-2 draw in the first leg of the quarter-final.
The 29-year-old has not made the trip with his teammates to St James' Park, and it remains to be seen whether he earns a recall to the XI for the second leg of the Europa League contest against Lyon next week.
The decision has opened the door for Altay Bayindir to make his Premier League debut for the club between the sticks.
Onana is not in the Man United squad vs. Newcastle
There is also major news in the Man United wing-back area, with Harry Amass making his full debut for the club.
The 18-year-old made his first appearance for the Red Devils as a substitute against Leicester City in the league on March 16, but he is given the nod to start as the left-sided wing-back at St James' Park.
Amass made the move to Man United from Watford in 2023, and he is regarded as one of the best young talents in England.
Victor Lindelof, Christian Eriksen and Joshua Zirkzee have also been introduced into the side, as Amorim makes changes following the Europa League quarter-final second leg with Lyon last time out.
However, club captain Bruno Fernandes starts despite suggestions that the influential figure could be rested.
Heaven back on bench for Man United
There is also a huge boost for the Red Devils on their bench, with Ayden Heaven back in the fold.
Heaven's season looked to be over when he picked up an ankle injury against Leicester before the international break, but the recent arrival from Arsenal has made a quicker-than-expected recovery.
Luke Shaw, Mason Mount and Kobbie Mainoo are also on the bench, with all three recently making their injury returns, while Patrick Dorgu is the player to drop out to allow Amass to come into the XI.
TEAMS
NEWCASTLE: Pope; Trippier, Schar, Burn, Livramento; Joelinton, Tonali, Guimaraes; J Murphy, Isak, Barnes
Subs: Dubravka, Wilson, Gordon, Targett, Krafth, Osula, Longstaff, Miley, Neave
MAN UNITED: Bayindir; Mazraoui, Lindelof, Yoro; Dalot, Eriksen, Ugarte, Amass; Garnacho, Zirkzee, Fernandes
Subs: Heaton, Heaven, Maguire, Shaw, Casemiro, Dorgu, Mainoo, Mount, Hojlund
Written by
Matt Law