Arsenal had done well to make an unbeaten start to the Premier League season but have won just one of their last three League matches, a 5-0 win against Sheffield United.
Having crashed out of the Carabao Cup in a 3-1 defeat to West Ham, the Gunners have now lost back-to-back matches in all competitions.
Of course, they may feel aggrieved after Anthony Gordon's 64th-minute goal stood despite a four-minute VAR check, which looked at three potential issues with the goal.
But they failed to create enough chances as both Kai Havertz and Bruno Guimaraes were lucky to avoid red cards.
Nizaar Kinsella assessed where the match was lost for the Gunners, who now play catch up on Manchester City and Tottenham in the title race.
Saka, Martinelli and Nketiah toothless
Bukayo Saka has been a sensation for club and country since he burst on the scene but is facing the first quiet spell of his career. It follows his first injury over the international break since his emergence on this stage.
The 22-year-old is now five games without a goal or assist in all competitions, having had a quiet night at St James's Park.
His struggles are also being felt across the frontline with Eddie Nketiah struggling to make an impact and Gabriel Martinelli being out-battled by Tino Livramento in the second half.
Arsenal did beat Sheffield United 5-0 last weekend but struggled to break down West Ham's low block in midweek.
There are signs Arteta's attack isn't as fluid as it was last season as he prioritises solidity this term.
Kai Havertz lost his head
His 37th-minute lunge was high and out of control. He risked receiving a red card but a yellow card was deemed enough as it was regarded as "reckless" rather than "dangerous" by officials.
On another day and with another referee he could have been sent off. Miraculously, he wasn't awarded a second yellow card for another late challenge on Miguel Almiron.
It was another game which passed Havertz by at Arsenal as everyone awaits signs he will be worth the £65million investment.
Arteta's iron-clad backline
The one positive despite Gordon's goal was the exceptional defending on show.
William Saliba may be one of the world's best central defenders right now and his team-mate Gabriel Magalhaes is proving his perfect partner.
The duo were put under relentless attack from Eddie Howe's dynamic pressing system, while balls in from Kieran Trippier were a constant threat against some physical forwards.
Ben White and Takehiro Tomiayasu also played well apart from the goal in a tricky away atmosphere at St James's Park.
It's little wonder Arsenal have the second-best defensive record in the league after Manchester City.