For Troy Deeney this was the night that his fondness for speaking his mind well and truly came back to kick him in the cojones. Always good for a soundbite, it was after this fixture in October 2017 that the Watford captain accused Arsenal’s players of lacking a certain male body part and outlined how he liked to “whack the first one” whenever the sides met.

Well, 18 months on, Deeney did indeed give an Arsenal player a whack and he was sent off for his troubles.

The flashpoint came early, after 11 minutes to be precise, and somewhat out of nowhere. Arsenal had just taken the lead through a combination of impressive opportunism by Pierre-Emerick Aubameyang and outright doziness by Ben Foster when the referee, Craig Pawson, was suddenly displaying a red card. Deeney was the guilty party having, it seems, been spotted by Richard West, the assistant on the far side, throwing his right forearm into the side of Lucas Torreira’s head as he ran past the Arsenal midfielder.

From where West was standing, it is possible he deemed that Deeney had hit Torreira with his elbow, with Pawson possibly coming to the same conclusion. As Javi Gracia was at pains to point out afterwards, that was not the case, yet there was no denying Deeney had been reckless and could have little complaints with what was his second ever Premier League dismissal and one that rules him out of Watford’s next three fixtures.

Deeney being Deeney he did complain, on the pitch and as he walked topless past the dugouts, with reports suggesting he swore at Unai Emery as he passed the Arsenal manager. Emery later confirmed the player did say something to him but did not confirm it was foul language and for the 30-year-old there followed the humiliation of hearing the away supporters take great delight in his absence as he watched the remainder of the first half in the players’ tunnel. A strong case of schadenfreude and, for Deeney, some comedown eight days after playing a crucial part in Watford’s remarkable FA Cup semi-final victory over Wolves.

“I don’t agree [it was a red card],” said Gracia. “Troy put his arm there but there was no contact with his elbow. I never saw an aggressive movement. I don’t understand why the referee took the decision.”

The Spaniard’s frustration was clear but he was also right to praise his team for how their reacted to the loss of their leader. As was the case at Wembley, Watford showed resilience in the face of adversity and created enough chances to feel they were somewhat unfortunate to suffer their first loss here since Boxing Day.

Craig Cathcart and the excellent Étienne Capoue both forced Bernd Leno into smart saves before half-time before Adam Masina clipped the bar with a swerving long-range drive on 62 minutes. And then, with time running out, Andre Gray went around Leno and appeared set to pass the ball into an open net only for Ainsley Maitland-Niles, on as a substitute, to produce an excellent block.

“To play with 10 players against Arsenal was demanding but we showed our spirit and character,” said Gracia. “My players deserve recognition.”

Despite the result, Emery was less effusive about his own side. Arsenal may have dominated possession and chances created but, as their manager said, they “lacked control” despite their numerical advantage. Yet in the end they did enough to secure a hugely important win – only their third in their last 13 away games in all competitions and one that moves them to fourth in this most intriguing of battles for Champions League qualification. The visitors also secured their first away clean sheet of the campaign.

Like Deeney’s sending-off, the only goal of the game arrived like a bolt from the blue – or should that be a bolt from mint green given Arsenal’s colours. They were on the back foot and seemingly rattled by Watford’s aggressive start when a rare surge upfield led to Daryl Janmaat being forced into playing a back pass to Foster under pressure from Aubameyang. The Arsenal striker chased the ball down and was rewarded for his efforts when Watford’s goalkeeper hit his clearance straight at his left foot and could only look on as the ball rolled into the net.

For Aubameyang it was a 23rd goal of the season while for Foster, usually such a reliable presence, it was a moment to well and truly forget. “I’ve said sorry to the lads,” he said afterwards. “I think I should have just Cruyff-ed him, but it’s not my style.”

In fairness to Arsenal, they showed plenty of spirit themselves in a consistently physical encounter and created chances to double their lead, with Alex Iwobi particularly threatening from an advanced left-sided position. On the basis of this display, the 22-year-old would be a decent bet to start Arsenal’s Europa League quarter-final second-leg against Napoli on Thursday.