Former Manchester United captain Roy Keane says the current squad lacks leaders and boss Jose Mourinho is unable to trust many of his players.
United are 19 points behind Liverpool in the Premier League table after losing 3-1 at Anfield on Sunday and following a poor start to the season which has seen manager Mourinho come in for criticism.
However, Keane, who was speaking to Sky Sports ahead of the Super Sunday clash, argued that it is the players, not the manager, who must take responsibility for their performances.
Keane said: "In my time at United, when you talk about trophies, you need, obviously, very good players. But I also felt we had really good characters, really good people. People you want to be in the trenches with.
"I still can't figure this United team out. The key, as well, to be a top player, is to do it week in, week out. I see United every few weeks and think, 'yeah they're looking not bad'. Then they look disinterested, which is no good for any of the big clubs.
"I think they've certainly lost their way and I look at the lack of characters, the lack of leaders in the team and you come unstuck, especially in the big games.
"When you're a manager or working on the sidelines you want to be able to trust most of your players. I don't think Mourinho has too much trust in a lot of United players.
"He made a point against Arsenal last week, when they drew and the standard of the game was really poor, he said in his interview after the game his big worry was every time the ball went in the box he felt like they were going to concede. If you're the manager sitting on the sidelines watching and you felt you were going to concede every time the ball went in your box, you're in trouble.
"So he definitely doesn't trust his back four. People say he's spent money on it, which he has done, but it doesn't mean to say [he trusts them]. They've made mistakes. They've got to go and purchase four defenders.
"But at some stage the players have to take responsibility for it. I know people say Mourinho has to get the fellas on side, but we're talking about a lot of international players here and if you're on that pitch and you're not looking after the ball or you're sloppy in possession that does come down to the player. At some stage your own pride has got to kick in, as a professional footballer."
Keane added that Mourinho's credentials as a manager should be respected and the players cannot blame him for their own poor form.
"We can talk about Mourinho all day but his CV warrants that he knows something about this game - absolutely outstanding. At some stage you've got to look at some of the players.
"A lot of them are international players, 25-26 years of age. They've got to take responsibility when they cross that line.
"I don't think I've ever gone out on the pitch and if I ever had a bad game looked at the manager and went 'that's your fault' or whatever about tactics and systems.
"Roll your sleeves up and do a job. And when the United players turn up today and put the United jersey on, embrace it, embrace the badge and the history, don't be thinking 'the manager is getting on my nerves'. Play the game. Do your job."
Sky Sports pundit Gary Neville was also critical of United's inconsistency this season.
However, the former Manchester United defender believes it could take some time for Mourinho to solve the problems he's facing.
"You don't know what performance you're going to get from game to game or within games actually, they can be awful in one half and good in the second half," said Neville.
"It's like they're crawling on their hands and knees minute by minute, week by week at the moment as a club. You can't be confident coming here today, other than the hope that actually, United have done well here over the last few years and you think of Jose Mourinho and the fact he can somehow galvanise performances and come here and get 0-0s and 1-0 wins and that's the hope you've got in the back of your mind.
"But you'd much rather have the Liverpool players in your team than the United players and to be fair the United players at this moment in time are so inconsistent, it's desperate. I don't know how they change it because it has been going on for a long, long time now."