Arsenal's hopes of qualifying for the Champions League suffered a fatal blow as Neal Maupay fired Brighton to a last-gasp 2-1 win after Gunners keeper Bernd Leno was stretchered off, while Watford snatched a late 1-1 draw against Leicester on Saturday.
In the first full weekend of English top-flight matches since the coronavirus shutdown in March, Arsenal's faint chances of finishing in the top four faded further.
Their cause wasn't helped by the controversial injury to Leno, whose screams echoed round the empty Amex Stadium after he slid awkwardly when he came to collect the ball just inside his own penalty area.
The German seemed to twist his knee and was given oxygen during several minutes of treatment.
Leno appeared frustrated with Brighton forward Maupay, shouting and pointing a finger at him while being stretchered to the tunnel.
Maupay had been the Brighton player challenging Leno for the ball when he fell.
Already hit by injuries to Granit Xhaka and Pablo Mari in their 3-0 defeat at Manchester City on Wednesday, Leno's departure was another blow to Gunners boss Mikel Arteta.
Ivorian winger Nicolas Pepe put Arsenal ahead in the 68th minute with a superb strike, the Ivory Coast winger cutting in from the right and curling into the far corner from the edge of the area.
But Arsenal's defensive frailties were exposed seven minutes later when Brighton defender Lewis Dunk stabbed home from close-range after Rob Holding's attempted clearance bounced off him.
Adding insult to injury for Arsenal, deep into stoppage-time Aaron Connolly helped the ball on to Maupay and he kept his head for a fine finish.
Maupay took a post-match swipe at the Gunners, saying: "Some of their players need to learn what is humility, especially one of them. He was talking all game, he was saying bad things.
"I don't want to say because I could be in trouble. I just said that this is what happens when you talk too much on the pitch."
Arteta's team are languishing in ninth place, eight points adrift of the top four, and may not even qualify for the Europa League.
Arteta didn't blame Maupay for Leno's injury, saying: "I think it was very unfortunate. I don't think he wanted to hurt him, but it is not looking good.
"It is unacceptable in the way we lost the game. The fact we missed so many chances and we did not compete for the second goal."
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