This was supposed to be the banker, the relatively easy one, at home against a team who had hit the magic 40 points and would be forgiven if they had sandals and sunglasses at the ready. Of all the hurdles lined up between Arsenal and their aspirations to reclaim a Champions League position via the domestic or European route, this was supposed to be straightforward. How wrong could they be.

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If Unai Emery was lulled into thinking he could afford to over-rotate, that notion was obliterated as a combination of Arsenal’s lamentable defending and Crystal Palace’s determination injected the afternoon with a pressure that left its burning mark. Roy Hodgson’s team capitalised on an underpowered and incoherent Arsenal line-up and wreaked havoc with their own power from set pieces. Arsenal’s 10-game winning streak at the Emirates evaporated at a costly moment. Emery rued that it was a “big frustration”.

Some of the responsibility lies at his own door, having picked a team comprising a mix of established and fringe players. There is a risk of sending too many Carabao Cup-esque squad members into the full glare of Premier League intensity and Emery’s gamble was exposed here. In such a situation, with the team already lacking some of its usual composure, it was extraordinarily bad timing for one of the more experienced players to implode. Shkodran Mustafi’s errors had a direct role in all three Palace goals. It felt all the more damaging as Arsenal’s defence had sharpened up enough lately, conceding only one goal in seven games, before this disintegration.

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Naturally Hodgson felt his team deserved plenty of credit for the way they executed their gameplan. “It was a very satisfying performance and we knew set-plays would be a weapon,” he said. “We had good delivery and players who are good at attacking the ball. I can’t say I am surprised. Arsenal’s strength is their fantastic play going forwards.” Direct comment about their defensive weakness was left unsaid but his team spoke loudly enough for him on that one.

Palace went ahead in the 16th minute, punishing Arsenal with ridiculous ease. Christian Benteke ran into the box blissfully unattended as Luka Milivojevic floated the ball in and the lack of awareness in the Arsenal defence was startling. Mustafi abandoned marking duties and allowed the striker to nod his first goal of the season – his first for almost an entire year – past Bernd Leno.

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The home crowd became fractious, worrying about the stakes. Their angst grew as Arsenal were denied a penalty shortly before half-time. Sead Kolasinac planted a cross towards goal which struck Aaron Wan-Bissaka on the arm. Jon Moss was surrounded by appealing Arsenal players but gave nothing.

Emery made a double change at half-time to try to repair some of the damage. The improvement was briefly encouraging. Arsenal wove their finest move of the match just after the restart and threw off the shackles to equalise. The goal belonged to Mesut Özil, architect and marksman. He found Alex Iwobi in space and the move flowed on to Alexandre Lacazette, whose deceptive pass was perfect for Özil. The finish was straight out of his personal playbook – dinking the ball in by chopping it into the ground first.

Back came Palace, aided by more chronic Arsenal defending. Another set piece was hoicked in and Mustafi inexplicably stalled like an old tractor. Wilfried Zaha unsurprisingly did not stop in sympathy and calmly guided the ball past Leno.

Facebook Twitter Pinterest Wilfried Zaha celebrates after putting Palace back in front Photograph: Michael Zemanek/BPI/Rex/Shutterstock

Hodgson was pleased for Zaha and sprang to the defence of a player caught up in a media story about leaving the club. “How many players, if the question is put to them, will say they don’t want to play Champions League football?” he asked. “Congratulations to the journalist, who has caught him at the right moment and extracted an honest answer out of him. Would you like to play Champions League football? Yes, I would. ‘Do you think you’re good enough to play at a higher level?’ He says yes. I don’t know what I can do to gainsay that. He’s certainly happy at Crystal Palace. That wasn’t the performance of a guy who wants to get away from his club. I would say quite the reverse. He’s on a four-year contract and I’m looking forward to seeing him in a Crystal Palace shirt for many years to come.”

Palace inflicted even more damage from another dead ball. Scott Dann’s header flew at James McArthur at such speed he did well to react and deflect the ball in. Arsenal were stunned and, even though Pierre-Emerick Aubameyang tried to instigate a rally with a solo goal, no more would come as Palace defended diligently to the end.

Arsenal now travel to Wolves and Leicester with it all to do to stay in the top-four chase. “I want to be positive,” Emery tried. “We were working to be in this key moment with the possibility to be in the top four and we are. Today be frustrated and tomorrow stand up. It is in our hands.”