NEWCASTLE, England -- Presumably Jose Mourinho was already grumpy after Manchester United's latest grim away performance, Sunday's 1-0 defeat at Newcastle. But the Old Trafford manager's mood might have darkened further if he heard Jamaal Lascelles, captain of the victorious home side, compare the St. James' Park unfavourably with Arsenal.

"I don't think they turned up today," said Lascelles, in response to a question about Newcastle's performance. "When you play against Arsenal and Manchester City you can really see their quality and, if you make one mistake or lack concentration, a goal will go in. Today I don't think they were at it, from the start of the game."

Ouch. It is one thing for United to be told by a player -- from a team that clambered their way out of the relegation zone with this victory -- that you're no good, but less threatening than Arsenal? That really stings.

Lascelles was right, though. Newcastle had something to do with their opponents' lacklustre showing, with pressing and harassing that forced mistakes and caused uncertainty, but the point is that Rafa Benitez felt emboldened enough to be aggressive against United, without fear his men would be overrun if they pressed too far.

A bit like citing Leicester's 2015-16 Premier League title as proof of what those outside the monied elite can achieve, using this season's soon-to-be champions Manchester City as an example of anything is a tricky business, because they're such an outlier as to render many comparisons pointless.

But it was notable that, when City came to visit at the end of December, Newcastle dug a virtual trench on the edge of their box and barely stuck their heads above it. That night was an exercise in damage limitation and, to a point it worked, in that they only lost 1-0.

There was no such caution against the side that, according to the league table at least, are the second-best in England. United weren't that bad: Alexis Sanchez was lively, while Romelu Lukaku did some smart things with the ball and, against a goalkeeper having an off day rather than the impressive debutant Martin Dubravka, Mourinho's men might have won 3-1.

But a season of unimaginative performances and the knowledge that they have a troublingly soft underbelly -- not something you'd say of United or Mourinho teams in years gone by -- gave confidence to a side threatened by relegation. Newcastle saw a chance and seized it with an ease that should worry everyone at Old Trafford.

Nor was his biting Arsenal comparison the end of Lascelles' withering assessment of United's performance.

"I think it was down to our pressing, being aggressive and on the front foot and obviously they didn't like it," he added. "I was at the back and could see their centre-halves on the ball and [they] didn't know what to do with it."

Jose Mourinho have lost their last two Premier League away games, failing to score each time. Getty

The defenders in question were Phil Jones and Chris Smalling, each of whom summed up United's inadequacy with isolated moments in the second-half.

First, the free kick from which Newcastle scored their winner was conceded when Smalling dived, pointlessly, in the middle of his own half after a heavy touch. Why do that? Even if you think simulation isn't a blight on the game and ultimately serves a purpose, what does it achieve to flop over in such scenario?

It spoke to a muddled mind, as did an incident in second-half stoppage time when United captain Antonio Valencia had to remind Jones to get back on the pitch so he could receive the ball from a throw-in.

You could argue that strident criticism is harsh, given there is only one club above them in the Premier League just happens to be among the most dominant for years. But something is wrong and there are clear problems with this United team.

Beyond those centre-backs, there is the question of how to fit in Sanchez when you've already got Anthony Martial, Marcus Rashford, Jesse Lingard and Juan Mata, as well as the ongoing "how to get the best from Paul Pogba" debate.

However, while those issues can be addressed on the training pitch, there seems to be a more fundamental -- perhaps more intangible -- problem: Opponents are not scared of United.

Granted, that might not have been the case since Sir Alex Ferguson retired, but the point is that little has changed in that respect since Mourinho arrived 18 months ago. And, at the very least, you would expect United's fear factor to be greater than that of Arsenal.