Arsenal's eighth loss since the turn of the year left them 13 points adrift of the fourth place that will secure automatic qualification for next season's elite and lucrative Champions League.
Lewis Dunk put Brighton ahead when he hooked the ball home from a corner after it dropped to him inside the six-yard box.
Arsenal has Nacho Monreal (back) and Alexandre Lacazette (knee) absent with Wenger likely to make changes with the Europa League trip to AC Milan looming. Glenn Murray made it two for Brighton less than twenty minutes later thanks to some truly dire defending by the visitors.
Xhaka has had his fair share of criticism from Arsenal fans this season but Henry praised the Switzerland global for his role in the Gunners' goal in the first half.
Throughout the game, Wenger sat in his chair, either shaking his head or staying quiet - much like I imagine the Arsenal board following the game -, while Chris Hughton barked his orders from the touchline.
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It was, however, to take just seven minutes for their frailties to be exposed by Brighton.
Arsenal were struggling to cope with Pascal Gross's movement, and sure enough, Gross played a pivotal role in Brighton's second goal, curling a sublime cross into the middle for Murray to head home.
It was almost 2-0 minutes later as Gross sent Cech sprawling to save at his near post, and Dunk headed over after 18 minutes from another corner by Gross. But an Arsenal team filled with such quality shouldn't be walking away from a mid-table game with nothing. With Arsenal's main concerns stemming from their defence, and both Mustafi and Cech to blame for the second goal of the afternoon, this wouldn't have given anyone hope moving forward.
Speaking at the post-match press conference, Wenger said: "I must tell you, honestly, at the moment my future is not my main worry".
Arsenal continued to press after the interval, with Mathew Ryan forced into a fine save to deny Mesut Ozil.
When Arsenal finally got a foothold in the game they couldn't do anything with it. But Arsenal were lucky to keep 11 men on the field when Sead Kolasinac, already booked, barged dangerously into Schelotto.