LONDON (Reuters) -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.
Arsenal have 51 points with City, who host Aston Villa on Sunday, on 45. The top two meet at The Emirates on Wednesday.
"Winning is about small margins. When you win you win by small margins. But if you cannot win it then you don't lose it," Arteta said. "We will get ready for City. It will be another big one and another beautiful one."
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.
"I said to the players before the game that we had to maybe have our best performance and I think we were close to that," Brentford manager Thomas Frank told reporters.
"You can't celebrate a point no matter who you play because we want to win but we could celebrate a very good performance.
"If there was to be a winner it should have been us today."
BELOW PAR
Arteta kept faith with the side that lost 1-0 at Everton last weekend but for the second week running his side were nowhere near their best.
They rode their luck in the first half with a well-drilled Brentford comfortable at the back and dangerous in attack.
The match was only minutes old when Rico Henry sliced horribly wide from a low cross.
Brentford then carved open the Arsenal defence again in the 24th minute when Bryan Mbeumo's cut-back was perfect for Toney but he fired against the woodwork with the goal gaping.
Arteta gathered his players around him and barked out instructions during one break in play and the home fans were grumbling when Ben Mee had another chance for Brentford.
Saka poked a shot from a tight angle at visiting goalkeeper David Raya and the hosts did finally put a flowing move together shortly before the break when Martinelli volleyed over.
Toney drilled a shot just wide after the break and Brentford looked set to rue their first-half misses when Saka slid a low pass across the area for Trossard to slot home.
Brentford were finally rewarded though as Toney headed in and a VAR check for offside found in favour of the visitors, a decision Arteta said he could not understand.
After scoring, Toney lifted his shirt to reveal a T-shirt in support of Sergi Canos, on loan from Brentford to Olympiacos Piraeus, whose mother died this week.
(Reporting by Martyn Herman; Editing by Toby Davis and Ken Ferris)