Glenn Murray equalized from the penalty spot in the 61st minute to cancel out an early spot kick by Pierre-Emerick Aubameyang and secure a draw that guaranteed Chelsea a top-four spot. The result effectively ended Arsenal's hopes of securing Champions League football through the domestic route.
Arsenal is three points behind fourth-place Tottenham, which also leads its north London rival by eight goals on goal difference. Chelsea is now four points ahead of the Gunners in third ahead of the final round of games next weekend.
Arsenal can still qualify for the Champions League by winning the Europa League, but this latest setback meant Unai Emery's first season in charge will most likely end in disappointment on the domestic level.
Emery's main task when he was hired to succeed Arsene Wenger was to bring Arsenal back into the top four, where it finished every year between 1997 and 2016 under the Frenchman. But the team has only garnered four points from its last six league games and came up with another disappointing performance at the Emirates on Sunday.
Aubameyang opened the scoring after Nacho Monreal was fouled just inside the box but the Gunners couldn't build on their advantage and allowed Brighton back into the game after the break by gifting the visitors an equalizer.
Henrikh Mkhitaryan gave the ball away just outside the Brighton area and Granit Xhaka then tugged at the shoulder of Solly March as he streaked into the Arsenal box after a quick counterattack. March went down to earn a penalty and Murray calmly converted from the spot.
Aubameyang missed Arsenal's best chance to restore the lead and the visitors nearly grabbed a winner when goalkeeper Bernd Leno had to palm away a close-range effort from March at the back post and Pascal Gross then blasted well off target moments later.
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