Arsenal have dropped into second place on the Premier League table after a stunning 3-0 defeat to Brighton on Saturday.
The Gunners were aiming to continue their perfect start to the season with victory at the Amex.
But the hosts took charge of the game from the referee’s whistle and went two goals up at the break.
Pascal Gross drilled in the opener before Charalampos Kostoulas doubled their advantage.
Chema Andres headed in Brighton’s third after the break to seal maximum points for Fabian Hurzeler’s team.
Manchester City can now go three points clear of Arsenal when they host Sunderland on Sunday.