The German made his debut in the EFL Cup win over Derby last month and has since displaced Simon Mignolet in the last three Premier League games.
But United legend Neville has Karius' performance in the 0-0 draw at Anfield last night, claiming he was easily intimidated by United striker Zlatan Ibrahimovic.
Neville said after the game: "He [Man United boss Jose Mourinho] would have looked at the vulnerability of goalkeeper Loris Karius.
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Loris Karius
REUTERS
Gary Neville slams Loris Karius performance against Manchester United
"He didn't look comfortable dealing with set pieces and seemed easily intimidated by Zlatan Ibrahimovic.
"Flapping at crosses will never instil confidence in your defensive team-mates and he's not the sort of keeper I would have confidence playing in front of.
"Make a decision and commit, be honest, just don't flap and put your team at risk."
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