London, Arsenal's new signing Leandro Trossard scored his first goal for the Premier League leaders but they 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 home Christian Norgaard's cross and stretch Brentford's unbeaten league run to 10 games.
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 21 games, reports AP.
Arsenal have 51 points with City, who host Aston Villa on Sunday, on 45. The top two meet at The Emirates on Wednesday.
Brentford, who are eighth with 34 points from 22 games, were full value for their point and exposed some worrying cracks in Arsenal's facade as the hosts pursue a first title since 2004.
Source: Bahrain News Agency