Pierre-Emerick Aubameyang struck his 13th Premier League goal of the season but a defensive error once again proved costly for Arsenal as Brighton recovered to claim a 1-1 at the Amex Stadium.
Aubameyang fired the Gunners in front after just seven minutes but Stephan Lichtsteiner’s failure to deal with a long ball forward handed Jurgen Locadia the chance to level 10 minutes before the interval with his his first goal since February.
Both sides had opportunities to secure three points in the second half but the visitors were left ruing the failure to close to within four points of third-placed Manchester City.
The opening stages had suggested Unai Emery’s team would have little trouble seeing off a Brighton side that had suffered three successive defeats.
It took Aubameyang less than four minutes to demonstrate his threat with the forward moving quickly into space to meet Matteo Guendouzi’s floated pass that dropped behind the Brighton backline.
Aubameyang’s reactions had taken him clear of the covering defenders and his first-time lob from outside the home penalty area almost caught out goalkeeper Mathew Ryan, who produced an outstanding, acrobatic save to tip the ball over the crossbar.
The following corner offered more signs of weakness in the Brighton defence when Arsenal centre-back Sokratis Papadopoulos was allowed to rise unchallenged and direct a header that was headed off the line.
Lewis Dunk’s red card at Bournemouth last Saturday meant Chris Hughton had been forced into a defensive rejig, with Shane Duffy partnering Leon Balogun at the heart of the Albion defence.
But it was clear the new-look defence would take time to settle in and a succession of errors in and around the Brighton box led to Aubameyang giving the Gunners a seventh-minute lead.
Two attempted clearances were charged down and when Balogun was caught in possession by Alexandre Lacazette in front of goal, Arsenal took full advantage.
Lacazette’s side-step wrong-footed Duffy and Balogun, giving him time to lay the ball off to the unmarked Aubameyang who produced a curling finish from the left side of the penalty area to beat Ryan.
Hughton’s side looked shaky but stood firm and began to assert themselves against the unconvincing visitors’ defence.
Glenn Murray thought he had forced a 24th-minute equaliser when he scrambled the ball home after meeting Martin Montoya’s cross but referee Anthony Taylor ruled the striker had kicked the ball out of keeper Bernd Leno’s hands.
But six minutes later Brighton did find an equaliser. The hosts were defending a corner but seconds later Davy Propper’s long pass was hopelessly misjudged by Lichsteiner, whose attempted header back to Leno fell short and Locadia nipped in and rounded the keeper before scoring.
Emery made a half-time switch in an attempt to fire up his side with Mesut Ozil being replaced by Alex Iwobi.
But neither side was able to find a way through and claim the points.