Quique Sánchez Flores had missed all of this – the thrills, the spills and the very peculiar madness that can turn Premier League football matches into the most gripping of spectacles.

The returning Watford manager watched his team lose their grip in the first half and Pierre-Emerick Aubameyang mete out the punishment with a pair of trademark finishes. The Arsenal striker now has five goals in five matches this season and his complete record at the London club bears consideration – he has 45 in 70 appearances across all competitions.

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Game over? Not at all. Not when Arsenal continue to treat the notion of defending properly with such disdain. Unai Emery’s team were the architects of their own downfall and their only fortune was that Watford did not depart with all three points.

Watford had the chances during a breathless finale when the outstanding Gerard Deulofeu fired inches off target and Tom Cleverley saw a shot deflect wide off David Luiz before, at the very last, Abdoulaye Doucouré blew a gilt-edged opportunity, shooting too close to Bernd Leno.

Arsenal’s fixation with playing short passes out from the back on goal-kicks had led to a couple of flutters, serving to transfer the momentum to Watford and, when they got it horribly wrong on 53 minutes, it provided the home team with a route back into the game.

Leno played a deadball square to Sokratis Papastathopoulos on the corner of the six-yard box but, when he looked for Mattéo Guendouzi, Deulofeu stuck out a boot and diverted it to Cleverley. The midfielder banged home a low shot.

Emery had switched from his midfield diamond to a 4-2-3-1 formation in an attempt to close out the final 20 minutes or so and there was something darkly comic about how his team were undone on the break for the equaliser.

Nicolas Pépé had been denied by Ben Foster but when Watford countered, Arsenal were exposed. More specifically, David Luiz was exposed. The Watford substitute, Roberto Pereyra, ran at him and, when David Luiz retreated, he entered his own area. Then, he hung out a leg at Pereyra and watched him tumble. It was a clear penalty.

Pereyra picked himself up to score and, although it should have been more in the end, Flores could enjoy a tangible reward from his first match back at the club that he managed in the 2015-16 season. One thing was plain. If Watford continue to play with such energy and character, they will soon rise from the foot of the division.

There was much for Flores to enjoy, not least the statistic that showed his team had rained 31 attempts at the Arsenal goal. They pressed remorselessly in the second half, suffocating their opponents, refusing to allow them to play.

But for Emery, the analysis was rather less kind. He was criticised for the decision to substitute Dani Ceballos on the hour and his explanation that it was a “very hot” day was merely one of his post-match comments that were difficult to understand. Ceballos, who had shown beautiful balance and perfect touches, hails from sunny Spain.

But the most scathing remarks concerned what happened in Arsenal’s defensive third, where Papastathopoulos and David Luiz had to bear the brunt of the responsibility. Graeme Souness, the Sky TV pundit, said Arsenal had played like a “semi-professional team” in the second half and it was difficult to disagree.

Emery had begun with a midfield diamond that featured Mesut Özil, playing his first game of the season, at the tip and Ceballos on the left and it was the latter who sparked Arsenal after a sloppy start.

Ceballos stretched into a challenge on Will Hughes and, when the Watford midfielder went down, his teammates stopped, inexcusably. It was hardly a given that a free-kick would be awarded. On the contrary. Sead Kolasinac did not stop. He charged forward, rolled the ball to Aubameyang and the striker did the rest, taking a touch, spinning and summoning power with minimal backlift to beat Foster inside the near post.

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Aubameyang would celebrate again shortly afterwards and this time, Özil was the creator. The weight on his pass that lacerated the Watford defence and freed Ainsley Maitland-Niles was perfect; the right-back crossed low and Aubameyang tapped home.

Watford had been the better team in the opening 20 minutes, when Cleverley extended Leno and José Holebas lifted wastefully over the crossbar, and they came to sense that Arsenal were vulnerable when playing out from the back. The visitors took tremendous risks and Guendouzi twice got away with it after giving away possession on the edge of his area. It was notable there were ironic cheers from the travelling fans on the rare occasion one of their players launched a clearance long.

Watford turned the screw after Cleverley’s goal. The substitute, Ismaila Sarr, rolled David Luiz and shot wide and Arsenal were left to cling on. The equaliser was the prompt for Watford to lay siege to the Arsenal goal but they could not find what would have been a deserved winner. Once again, there were grave questions about Arsenal’s mental toughness. Emery has much to ponder.