Joao Pedro scored a second-half penalty to dent Arsenal’s title hopes as the Gunners were held to a draw by Brighton.
Arsenal went ahead in the 16th minute through Ethan Nwaneri, who was starting just his second match in the Premier League.
The 17-year-old was involved in a clever move with Mikel Merino and Declan Rice before firing a shot that squirmed past goalkeeper Bart Verbruggen and found the far corner.
Arsenal dominated as they looked to build a bigger lead, and they were to pay for not taking their chances when Pedro struck from the spot just after the hour.
The penalty was awarded for an unusual incident when Pedro flicked the ball up and William Saliba, in attempting to nod it away, made contact with the head of the Brazilian forward who went to ground.
The foul was checked and confirmed by the video assistant referee, who deemed there was sufficient contact for a penalty and Pedro then sent David Raya the wrong way to level the scores.
It could have got worse for Arsenal after that, with Brighton substitute Yankuba Minteh curling wide from inside the area when well placed.
The result leaves Arsenal five points behind leaders Liverpool with Mikel Arteta’s side having played two games more.