The destiny of both clubs this season may yet be shaped by events in the 50th minute of a remarkable match that featured one of the finest comebacks ever witnessed in the Premier League. Arsenal were leading 4-0, heading for their seventh successive win and apparently in the mood to sustain a challenge to the leaders Manchester United.
In contrast, hundreds of Newcastle United supporters had already left the ground, disillusioned by the sale of Andy Carroll and an abysmal first-half performance that revived relegation fears. Then Joey Barton put in a strong challenge on Abou Diaby, who reacted by going after the midfielder and pushing him to the ground. Kevin Nolan then arrived and the Arsenal midfielder also pushed him away.
Referee Phil Dowd showed Diaby a red card and the match was transformed, with Barton adding to Arsenal's anguish by emerging as the dominant figure in Newcastle's fightback. He scored twice from the penalty spot, Leon Best was also on target after having an earlier goal disallowed for offside, and Cheik Tioté powered in a fittingly spectacular equaliser in the 87th minute.
Arsène Wenger, the Arsenal manager, accepted it was a second half that may hurt their title aspirations. "Psychologically, dropping two points like this is very damaging," he said. "I cannot measure how angry I am. It's very frustrating because this was a good opportunity to take three points. I knew, though, that the game was not won at 4-0 because Newcastle kept fighting."
Wenger refused to criticise Diaby for the red card that changed the balance of power. He insisted: "It was an unlucky sending-off and Joey Barton was very lucky to stay on the pitch because of the nature of his tackle.
"Diaby was having an outstanding game, but he lost his nerve because he has suffered so many bad tackles. That tackle provoked his reaction."
Arsenal's Jack Wilshere vented his fury at the referee on Twitter, writing: "Inconsistent refereeing needs to stop. It's killing the game. If Diaby is sent off, what's the difference between that and Kevin Nolan's challenge on our keeper!?"
Newcastle's manager Alan Pardew disagreed with Wenger: "This is football in the Premier League. I have no problem with the challenge and Mr Wenger needs to see it again. Joey didn't react, he didn't get up – and the Joey of old would have done that. In that little moment, he showed why some people are thinking that England call might be coming his way. He has matured as a person."
Before the red card, Arsenal were in control and needed only 26 minutes to equal the four goals they scored here in the Carling Cup earlier this season. Only 44 seconds had gone when Theo Walcott held off Fabricio Coloccini's unconvincing challenge to move on to Andrey Arshavin's through-ball and put Arsenal ahead.
The second goal was only delayed a further two minutes and Newcastle's central defenders were again at fault as Johan Djourou headed home Arshavin's free-kick.
Now it was time for Robin van Persie to become the tormentor-in-chief as the first chants directed at Newcastle owner Mike Ashley were heard. Van Persie turned in Walcott's right-wing cross in the 10th minute, then headed in Bacary Sagna's pass from the same area with 26 minutes gone.
Indeed, Newcastle could count themselves fortunate not to be further behind at the interval. Even Pardew did not sense a comeback was on the cards until Arsenal went down to 10 men and Tioté had the final say with a splendid 30-yard shot. "It was an incredible day," said Pardew. "Anyone watching it could pick lots of things that were wrong, but it was really great. It was not about tactics, it was about what's inside you and the character you've got.
"I cannot praise the players and the fans enough. Even at 4-0 down, the fans didn't give us a monster bad time. There were some boos, but what would you expect? I thought the house might come down, but we all turned it round. Now it's about being strong until the end of the season and showing character. We showed it today in abundance and I'm so proud of them."
Referee: Phil Dowd
Man of the match: Barton