Neal Maupay piled the misery on Arsenal with a last-gasp goal to give Brighton a 2-1 win over the Gunners, who had earlier seen goalkeeper Bernd Leno stretchered off.
Replays showed Leno had appeared to see his knee buckle after being pushed by Maupay as the two competed for an aerial ball before half-time, and the German 'keeper had aimed some choice words at the Brighton forward as he was stretchered from the pitch.
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- Mikel Arteta: Brighton defeat all our fault
- Neal Maupay 'Sorry for Leno; Arsenal need to learn humility'
The Gunners put their disappointment behind them to take the lead after the break, with Nicolas Pepe curling in a stunning opener after 68 minutes.
But their joy was cut short when Lewis Dunk slid in to bundle home an equaliser from close range following a corner seven minutes later, and in the fifth minute of added-time, Maupay ended a controversial afternoon with the winning goal, running onto Aaron Connolly's one-two before lifting the ball over replacement goalkeeper Emiliano Martinez.
Brighton: Ryan (7), Schelotto (5), Webster (7), Dunk (7), Burn (7), Bissouma (8), Propper (5), Mooy (6), Gross (6), Maupay (7), Trossard (5).
Subs: March (7), Montoya (6), Connolly (7), Stephens (n/a), Mac Allister (n/a).
Arsenal: Leno (6), Bellerin (5), Mustafi (6), Holding (6), Kolasinac (6), Pepe (7), Ceballos (6), Guendouzi (5), Saka (7), Aubameyang (6), Lacazette (5).
Subs: Martinez (6), Nketiah (6), Willock (n/a), Tierney (n/a), Nelson (n/a).
Man of the match: Yves Bissouma
Brighton's first league win of 2020 gives them breathing space in the fight against relegation with a five-point cushion over the bottom three, while ninth-placed Arsenal, who had not lost this year prior to the Premier League restart, could end the weekend in the bottom half - and as many as seven points off the Champions League qualifying spots.
Maupay magic seals miserable Arsenal return
A fluid Arsenal formation kept Brighton on the back foot in the opening stages, with Bukayo Saka and Hector Bellerin causing problems as free-roaming wing-backs.
Saka in particular enjoyed life up against Ezequiel Schelotto, and almost provided the breakthrough when he turned inside and cracked a powerful effort against the bar from 20 yards.
Brighton recalled Ezequiel Schelotto and Pascal Gross from the side which drew with Wolves before the coronavirus break.
Arsenal made five changes from Wednesday's defeat to Manchester City, recalling Nicolas Pepe and Alexandre Lacazette, but left Mesut Ozil on the bench.
Alexandre Lacazette should have done better on the half-hour when Saka turned provider from the left flank, but gave Mat Ryan the chance to make a smart but simple save from his downward header.
The standout moment of the half would follow in completely innocuous circumstances, as Maupay led with his body to challenge Leno when the goalkeeper collected a long ball forward, before seeming to jar his knee on landing and, minutes later, being stretchered off.
Replacement Martinez was called into action moments after coming on to hold Aaron Mooy's stinging drive from a corner in Brighton's only shot on target of the first 45 minutes, but 10 minutes into the second, they had another as Maupay's effort from a tight angle was turned behind.
Arsenal continued on the front foot but lacked the sufficient spark to make the breakthrough until Pepe turned on the style with the sort of magic he became known for before his move from Lille last summer, turning inside off the right and bending a shot over Ryan for the opener.
Only seven minutes later, the Gunners' hopes of kicking on from the restart were already dealt a set-back, when Solly March's delivery from a corner was turned goalwards by Maupay and blocked on the line, only for a sliding block from Dunk to turn the ball home.
A raft of substitutions in the final 10 minutes from either side threatened to take the sting out of the game but there was one moment of drama left, as Maupay exchanged passes with Connolly on the edge of the Arsenal box before beating Martinez with a smart finish.
His own joy turned to anger at the final whistle as a disagreement with Mateo Guendouzi turned sour when the Arsenal man appeared to put his arm out while Maupay was running past. A mass confrontation followed between both teams as tempers flared from the Gunners, whose frustration at losing both games since the Premier League restart became increasingly apparent.
What the managers said...
Graham Potter: "There's no crowd to help the players, they have to find it themselves within, we've spoken a lot about it and how we keep going to the end regardless of what's happening and we got the rewards for that today.
"When you conceded a last-minute goal, emotions are raw, it's hard for us to contain our excitement, we're fighting for our lives, and it's disappointing for them, they played a good game and I don't think they deserved to lose but sometimes life isn't fair and you have to deal with it, I think you just saw that emotion - it's not a big problem."
Mikel Arteta: "I'm not concerned about our character, but how we compete in the Premier League match. It's 100 minutes in this case, every ball, every action, the moment you lose concentration the opponent is going to punish you, it's not the first time it's happened, and if you want to win matches consistently at this level that's a must - it's non-negotiable.
"I think they competed for a large part of the game, but in crucial moments when you don't, you pay the price. It's my fault as I'm the one who has to make sure they do.
"I think no player has the intention to hurt anyone, I think it's the same here, it's unfortunate. Bernd's injury doesn't look good, it can happen, we'll analyse it tomorrow. We think he had a hyperextension of the knee and we'll have to assess the damage."
Man of the match - Yves Bissouma
No-one made more tackles (6), interceptions (2) and won possession (10) back more on either side than Bissouma, who was a real engine for Brighton and only outrun by Maupay, Burn and Propper.
The Malian midfielder put in a great shift for the hosts and played a major part in stopping Arsenal dominating in the middle of the park, even when they tucked Saka and Bellerin inside.
Brighton travel to Leicester on Tuesday night, live on Sky Sports Premier League from 5.30pm; Kick-off at 6pm.
Arsenal have a couple of days more rest before they head to the south coast to face Southampton, also live on Sky Sports Premier League from 5.30pm; kick-off at 6pm.