United is now 19 points behind Juergen Klopp’s Premier League leader and sits 11 points off fourth place and Champions League qualification, Reuters reported.
But while the numbers speak for themselves, Neville and Keane, both working as analysts on Sky Sports television, suggested the club’s problems ran much deeper than just its current league position.
Mourinho’s decision to leave Paul Pogba as an unused substitute raised eyebrows with Neville saying the midfield was not up to scratch.
“I can’t get over United’s central midfield. If you’re Paul Pogba watching (Nemanja) Matic, (Ander) Herrera, (Marouane) Fellaini, Fred, who played the other night ... not one of them can pass a football,” he said.
“None of them can actually receive the ball and pass the ball. I just find it absolutely staggering. I thought United were awful today....It’s not good enough,” added the former fullback who won eight titles in Sir Alex Ferguson’s team.
Neville said it would not make sense to sack Mourinho midseason and pointed the finger at the club’s directors for extending the manager’s contract last season.
“The board are so naive, giving him a new contract. Manchester United need to reset. It’s not just the manager, it’s deeper than that. They lost control of the football club when they gave him a contract extension 18 months in.
“The minute he came back from preseason he was at it and the club lost control. There is not that experience or knowledge in the football club above him to be able to manage or control him and handle him.”
Keane said he was not surprised by the performance he witnessed at Anfield.
“I looked at United and thought they’re going to be found out today. And they were.
“It’s a huge concern going forward. I certainly believe a lot of their players are not good enough to be playing for Manchester United. They’re good players but not good enough for Manchester United.
“They’re so far behind the likes of Man City, Liverpool, Tottenham and Chelsea. The biggest problem is defensively; you have to have some foundation to go forward. They look like they’re all over the place.”
The Irishman suggested that Pogba might not have a long-term future at the club.
“If he’s sitting on the bench and not getting on, you’re thinking his days must be numbered. I don’t think they’ll do anything in January but, come the summer, you move him on.”
Keane speculated that the mood at the club may not be conducive to success.
“Looking at Mourinho on a match day, I’d love to know what the atmosphere is like at the training ground,” he said.
“Is it a happy camp? Because seeing the players’ body language, I don’t get the impression they enjoy playing for Man United. Some of them look disinterested. Is that coming from the manager?”