Arsenal missed the chance to go third in the Premier League table after they were held 1-1 by Crystal Palace on Sunday.
Alexis Sanchez put the hosts ahead at the Emirates on the stroke of half-time with his third goal in as many games, and the hosts squandered several opportunities before Yannick Bolasie secured a point.
The Palace winger cut inside on 81 minutes and caught Petr Cech by surprise with a low drive from the edge of the box that found the corner.
The visitors could have won the game when substitute Wilfried Zaha capitalised on an error from Laurent Koscielny, but a last-ditch tackle from Gabriel bailed out his team-mate.
The result leaves Arsenal looking over their shoulder in the race for a top-four spot, with Manchester United just four points behind them in fifth place.
Meanwhile, Crystal Palace remain 16th and extend their unbeaten run to four Premier League matches.
Arsene Wenger brought Cech back into the side after Arsenal's 3-3 draw at West Ham, and the Gunners goalkeeper was the first to be tested.
Even then, the first shot on target didn't come until the 28th minute in a low-key start, but Cech comfortably gathered Bolasie's hopeful strike.
It opened up as half-time approached, and both sides had opportunities before Sanchez opened the scoring.
Connor Wickham headed Yohan Cabaye's free-kick over the bar for Palace, while Wayne Hennessey smartly denied Mesut Ozil after a neat one-two with Sanchez.
The Chilean broke the deadlock in first-half stoppage time, holding off the challenge of Pape Souare and heading over the Palace 'keeper after a measured chip from Danny Welbeck.
It was only Arsenal's second attempt on target in a lethargic opening half as they controlled more than 75 per cent possession but laboured in the north London sun.
And they missed several chances after the break to extend their lead, with Alex Iwobi and Welbeck both guilty.
The former fluffed a header after a fine cross from Francis Coquelin, before Welbeck struck straight at Hennessey with Ozil and Sanchez waiting for the cross.
Ozil then sent a free-kick narrowly wide as the Gunners pushed for a second, and Hennessey saved bravely from Welbeck after a poor clearance from substitute Emmanuel Adebayor.
Palace served warning of their threat when Bakary Sako's header forced a fine stop from Cech, but the Arsenal 'keeper will not look back fondly on the visitors' winner.
With nine minutes to play, Bolasie was shown onto his right-foot and his firm strike squirmed past Cech to level.
Arsenal piled forward in search of the winner, but Palace had the best opportunity to steal the victory in stoppage time. A mistake from Koscielny allowed Zaha into the penalty area, and only Gabriel's covering tackle denied Adebayor a tap-in.
Boos for the home side were audible at the final whistle following Arsenal's second straight draw, and the dropped points mean they face a battle to hold onto a top-four spot with five games remaining.
Player ratings
Arsenal: Cech (5), Bellerin (6), Koscielny (5), Gabriel (6), Monreal (6), Coquelin (6), Elneny (6), Sanchez (7), Ozil (6), Iwobi (6), Welbeck (6)
Subs used: Walcott (6), Giroud (6), Ramsey (6)
Crystal Palace: Hennessey (7), Ward (6), Dann (8), Delaney (8), Souare (6), Puncheon (6), Jedinak (7), Cabaye (7), Ledley (6), Bolasie (7), Wickham (6)
Subs used: Sako (6), Zaha (7), Adebayor (6)
Man of the match: Damien Delaney