New signing Leandro Trossard scored his first goal for Arsenal but the Premier League leaders were left frustrated as Ivan Toney secured a deserved 1-1 draw for Brentford on Saturday.
The Belgian forward replaced Gabriel Martinelli just past the hour mark with his side struggling and made an almost instant impact to convert a low cross by Bukayo Saka.
An eight-point lead in the table beckoned for Mikel Arteta's side but they never looked comfortable against an enterprising Brentford who should have been ahead by halftime.
Toney, guilty of missing a sitter in the first half, pounced in the 72nd minute to nod in Christian Norgaard's cross.
Despite dropping points for the second week in a row, Arsenal lead the table by six points from champions Manchester City with both clubs having played the same amount of games.
Arsenal have 51 points from 21 games with City, who play Aston Villa on Sunday, on 45. Arsenal and City then face each other on Wednesday in what could be a crucial match in the title race.
Assessing the performances from the Emirates Stadium, Olakunle Afolabi provides his player ratings in the photo gallery above. To move on to the next photo, click on the arrows or swipe if using a mobile device.