Despite an impressive start to the season, Jürgen Klopp’s side are yet to keep to a clean sheet in the league, conceding 10 goals in their opening seven games.
Three of those strikes have come from set pieces. In total, Liverpool have conceded 16 set-piece goals since Klopp's arrival last October.
Jose Mourinho's United squad is among the tallest in the Premier League, with an average height of 6ft, and Neville believes this size advantage could prove pivotal.
“The big weakness for Liverpool on Monday is set pieces,” he told Sky Sports. “If United put the ball in the box around the goalkeeper and the back four there's going to be problems.
“That's the way Liverpool are at the moment. Even against Arsenal in the first game of the season it was 4-1 and Arsenal made it 4-2 and you could see Jürgen Klopp on the sidelines thinking 'do I quite trust these?'”
Liverpool have since held out to pick up three points at Chelsea, where they successfully protected a 2-1 scoreline for the final 29 minutes.
Although he believes that victory was a “big, big moment” for Klopp’s men, Neville still sees the Merseysiders’ defence as a potential weakness.
“To come through it when it was 2-1 was a big moment to give them the confidence that they can actually hold on to a lead. They did it at Arsenal as well, but they still look a little bit weak defensively.
“It might not play out in the goals they concede, but it feels to me like from 60 minutes to 90 minutes they tire a little bit and dip. That's where it feels like United could get on top.”
Louis van Gaal’s United left Anfield with maximum points last season after Wayne Rooney scored following a late corner.
Klopp’s Liverpool took their revenge in the Europa League, however, eliminating Van Gaal’s United from the round-of-16 with a 3-1 aggregate win.Reuse content