Manchester City slipped to defeat at home on Saturday evening, beaten 1-0 by Brighton in front of their own fans at the Etihad Stadium in the ninth round of the Premier League.
Yasin Ayari, the Sweden international of Tunisian origin, settled it with the only goal of the night in the 11th minute.
City huffed and puffed for 90 minutes but never found a way through Brighton's resolute defence. It was a second successive league defeat for Pep Guardiola's side.
For Brighton, it was sweet revenge. City had dumped them out of the Carabao Cup only last Wednesday, winning 4-3 on penalties.
The result leaves City stuck on 21 points at the top of the Premier League, and their lead is now under threat from Arsenal. The Gunners sit level on points and face Liverpool on Sunday.
Brighton, meanwhile, climb to 19 points and third place in the table.