Yannick Bolasie struck late for Crystal Palace to secure a draw in a match which Arsenal completely dominated.
Arsenal should have won comfortably to leapfrog Manchester City into third but instead they remain fourth in a nervy race for a Champions League spot.
Alexis Sanchez headed in Danny Welbeck’s chip to give the Gunners the lead but they lacked a killer instinct to put the result beyond doubt.
Bolasie then struck from distance, beating Petr Cech at his near post.
The Congolese forward’s equaliser alarmingly sucked the energy out of Arsenal and it was their London rivals who seemed more likely to score in the dying minutes.
Wilfried Zaha had the home defence backpedalling with a surging run into the box, but luckily for the Gunners a heavy touch from the winger allowed Gabriel to nick the ball.
It was a performance which summed up Arsenal’s season. They missed a number of opportunities, had more than 70% of the possession but once again failed to secure three points in a match they were expected to win. BBC Sport