Mikel Arteta's biggest mental barrier held Arsenal back once again from stamping themselves as serious contenders for the 'fourth and final' Champions League spot.
The Gunners launched themselves into the action at Old Trafford and began in the ascendancy, pinning Manchester United back and suffocating the Red Devils often to the confinement of their own half.
But, as Arsenal continued to apply pressure and force the home side onto the brink of submission, Emile Smith Rowe's opener burst a psychological bubble that saw United bolt out of the gates.
Like a catapult, the north London side had been pulling back the elastic band but once they let go to open the scoring, the band flung back in their faces.
Arsenal had seemingly retracted their attacking threat, slowly retreated into their own defensive third and looked to absorb the pressure without hesitation.
Arteta's side have become renowned for their willingness to almost surrender their dominance once they go ahead, hampering the Gunners' ability to compete for a top-four finish.
Whether it's anxiety, inexperience, a lack of camaraderie, confidence in one another's ability, or maybe lack of instruction communicated by Arteta; there is a mystery factor that has infected the Arsenal squad that causes them the naturally recline and invite a reply from the opposition.
By retreating into the safety of their own half the Arsenal players are gradually reliving themselves of as much defensive responsibility despite having shown that they've got the tools to operate under Arteta's system to an elite standard.
The Gunners struggle to sustain their boss' demand of pressing high, controlling the game and winning the ball back as high up the pitch as possible but because of their physical inability, but psychologically.
This infectious doubt that is shared among Arteta's side stems from the notion that the Gunners simply lack a figure who has worked in a similar system, has a wealth of tactical experience and can help dictate and orchestrate the side through various phases of fixtures.
Emile Smith Rowe and Bukayo Saka, who have done an excellent job at leading Arsenal so far, don't have the tactical experience that an older player or someone who's worked in a similar system to Arteta's before will have.
But, the young duo need a voice behind them on the pitch to guide them - and others - through mental battles when they're inclined to retract their high-line.
A prime example of this is Chelsea's acquisition of Jorginho under Maurizio Sarri in 2018 and Pep Guardiola's use of Fernandinho; two of Europe's most tactically astute footballers who understood the principle of their boss' game plan.
They were each able to become generals on the pitch and grow into pace-makers for their respective sides and, while Arteta has some exciting options in midfield already, Arsenal need an aggressor that keeps the Gunners on the front foot with the Spaniard's tactical objective at forefront of their mind.
Granit Xhaka, Albert Sambi Lokonga or Thomas Partey could grow into said role but the north London side need to sign a 'Jorginho or a Fernandinho-type' player to ensure Arteta claims a top-four place but ultimately eases the stress on Smith Rowe and Saka.
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