Arsenal's hopes of a top-four Premier League finish took another blow as they were deservedly beaten by Brighton following a lacklustre display.
Enock Mwepu was the star of the show for the visitors, creating Leandro Trossard’s opener before his own fine strike doubled the lead. Martin Odegaard’s late consolation meant Brighton left with a deserved 2-1 win.
Arsenal were already reeling from a 3-0 loss at Crystal Palace on Monday night and, with Kieran Tierney and Thomas Partey missing through injury, their small squad was exposed once more.
Gabriel Martinelli had a goal ruled out for offside but other than that the Gunners rarely threatened and lost more ground in their hopes of returning to Champions League action.
Brighton travelled to north London having ended a six-game losing streak with a goalless home draw with rock bottom Norwich last weekend.
However, Graham Potter has history of winning on this ground and he once again proved a thorn in the side of Arsenal, who now face a trip to Southampton next weekend.
The mood at the Emirates Stadium has been better of late but, with the chastening defeat at Palace still fresh in the memory, there were grunts and groans at the earliest of errant touches.
It was a slow start with neither side creating many chances, although Gabriel Magalhaes should have done better with a close-range header from a Bukayo Saka free-kick.
But it would be Brighton who would go ahead, Trossard slotting home a low Mwepu cross following a good team move just before the half-hour mark.
The goal came down Arsenal's left, something that would not have gone unnoticed by Arteta following his selection, which saw back-up left-back Nuno Tavares dropped despite Tierney’s absence as Granit Xhaka deputised instead.
Arsenal thought they had levelled on the stroke of half-time but Martinelli’s point-blank header was ruled out after a lengthy VAR check deemed the forward to be offside.
Arteta made no changes at the interval but, with chances still proving to be at a premium, he turned to Eddie Nketiah on the hour.
Instead the task became harder as Brighton deservedly doubled their lead.
The impressive Mwepu topped off an eye-catching outing by driving home from the edge of the box after a neat interchange from Trossard and Moises Caicedo.
Club-record signing Nicolas Pepe was next to come on for Arsenal but their players seemed confused by the set-up as a speculative Albert Lokonga strike whistled past the post.
It looked like Arsenal were destined to end the game without a goal but they halved the arrears through Odegaard.
The Norway captain had just rattled the crossbar with a free-kick, with Nketiah’s follow-up hitting the same piece of woodwork, before his looping strike hit former Gunner Danny Welbeck and beat Robert Sanchez.
The Spanish goalkeeper then clawed away an Nketiah diving header as Brighton saw out the closing stages to seal just their third league win of the calendar year.