#1 Brentford's off-colour performance in the first half
While the Championship side came into their own after their first and only goal in the 58th minute, they exuded signs of a skittish mindset before that. These nerves helped Arsenal put their foot on Brentford's throat and Welbeck pressed hard with his brace in the first 45 minutes.
Iwobi and Mkhitaryan caused problems from the wings, Matteo Guendouzi showed off his long-range passing, and the Gunners' backline held its own in the limited times that tested them in the first half.
While Brentford managed to come into their own later in the match, it was almost of out of their hands by then. Arsenal, on the other, capitalized on their strong start and stood their ground under consistent attack in the last quarter of the game.