The Gunners suffered a setback in their bid to win a first Premier League title since 2004 after a subdued performance at their bitter rivals.
United teenager Marcus Rashford scored twice on his Premier League debut to hand the hosts a 2-0 lead before Danny Welbeck reduced the deficit ahead of half-time.
Ander Herrera restored the home side’s two-goal cushion before Mesut Ozil scored what ultimately proved to be a late consolation for the visitors.
Speaking on Match Of The Day 2 on Sunday night, former Arsenal striker Wright pinpointed where the north London side went wrong.
“Arsenal’s main attacking players – the likes of Mesut Ozil, Alexis Sanchez and Theo Walcott – all struggled to get going,” Wright told BBC Sport.
“So it was one of those games where the Gunners had to stay solid at the back, but they were poor in that department for Marcus Rashford’s first goal.
“That got United going – as soon as they scored they seemed to realise ‘Arsenal are not up for it today’ and you could see their confidence grow.”
Arsene Wenger’s side lost ground to Leicester City and Tottenham Hotspur in the title race after their rivals secured late Premier League wins at the weekend to compound the Gunners’s misery.
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