It should have been the day when Arsenal stamped their authority on the Premier League with a commanding performance against a weakened Manchester United.

Having seen Leicester score a last-gasp goal the previous day, a win was the only acceptable result.

But yet again Arsenal left Old Trafford without any points and with familiar failings resurfacing at the worst possible time.

Being five points off top spot doesn’t mean Arsenal are out of the title race. But it is the manner of the defeat which is most deflating.

Since the beginning of the year, Arsenal have produced a series of performances unbecoming of potential title winners.

Only once, the late win against Leicester, have Arsenal done something which made you think that a title win was a serious possibility.

For all the talk of mental strength within the squad, the players have a chronic ability to fail when the pressure is on. Naivety, sloppiness and ineptitude spreads through the team like a disease. When fans question the passion and desire, it can feel like a cliché. But when you see that Theo Walcott had zero shots on goal, created no chances and touched the ball just 17 times in 63 minutes, his lack of commitment must come under scrutiny.

For a player so desperate to be a striker, those statistics are appalling, bordering on scandalous. The most damning indictment of Walcott’s display was Arsene Wenger’s effusive praise of United’s two-goal hero and recent debutant Marcus Rashford.

He said: “The player who was surprising for me is Rashford. The timing and intelligence of his movement was great.”

In Walcott’s defence, it’s a long time since Arsenal were at their free flowing best. Usually when Wenger has come under fire, he has always had great attacking football to fall back on as a reason to keep faith.

But goals have been hard to come by this season throughout the team as they’ve struggled for cohesion and most worryingly, technical quality.

While he isn’t the answer to all Arsenal’s woes, the absence of Santi Cazorla to set the tempo and make use of the football, is a glaring problem.

However, the most concerning aspect of Arsenal’s recent matches is their mental attitude. The ability of the team is unquestionable but their flakiness has never been solved despite the squad evolution in the past 10 years.

The only common denominator in that time is Wenger. For so many of his sides to be weak mentally is perplexing and reprehensible.

Sunday’s damaging defeat has left Wenger’s critics with plenty of ammunition and even his staunchest of supporters are having trouble coming up with a convincing reason for him to stay if he suffers the embarrassment of losing the title to either Leicester or Spurs.

This weekend’s north London derby is arguably the biggest of his entire tenure. Lose and the title will most likely be gone and any backing he had will disappear. Win and hopes will be raised again.

The title is what’s demanded and Arsenal simply have to be successful otherwise Wenger’s position will be verging on untenable.

Follow me on Twitter @UcheAmako