Reigning champions Arsenal came from behind to beat big-spending Chelsea in a pulsating London derby at Emirates Stadium.
Chelsea stunned the home fans by taking a second-minute lead through £117m summer signing Morgan Rogers' volley after the Gunners failed to clear Reece James' free-kick.
That was the first goal Mikel Arteta's side had conceded this season.
Despite their flying start, Chelsea had not kept a clean sheet in their previous 18 Premier League games and Xabi Alonso's side were forced to withstand wave after wave of Arsenal pressure.
Emiliano Martinez denied Bukayo Saka, while Jorrel Hato and Wesley Fofana each made crucial blocks before the Gunners levelled in the 25th-minute after former Chelsea forward Kai Havertz beat Martinez at his near post with a well-placed finish.
In a high-quality match, Chelsea - who spent close to £350m in the summer transfer window - came within a whisker of retaking the lead.
After captain James had forced David Raya into a save from outside the box, Pedro Neto hit the post after a wonderful solo run before Martin Odegaard settled it in the 50th minute.
The Arsenal captain beat Martinez after Havertz's clever dummy, the Norwegian's second goal in three Premier League games.
Chelsea substitute Estevao thought he had equalised right at the end of the game but Raya produced a brilliant finger-tip save as the Blues lost for the fifth straight league game at Emirates Stadium.
BBC