Mikel Arteta looked like he had seen a ghost. With his side leading 2-0 against Aston Villa thanks to goals from Gabriel Martinelli and Kai Havertz, the Arsenal manager must have felt they were within touching distance of a cathartic victory that would keep up the pressure on Liverpool.

But having seen the Premier League leaders seal a dramatic late victory over Brentford earlier in the afternoon, once again Unai Emery had other plans against his former club. Arteta could only watch on in horror as Youri Tielemens pulled one back before Ollie Watkins volleyed home the equaliser to the delight of the Villa supporters and their manager, who celebrated wildly at the final whistle as he did back in March after a 2-0 victory here that eventually proved terminal to Arsenal’s title challenge last season.

Even when it seemed they might have won it late on through Mikel Merino, Arsenal’s joy was short-lived as VAR ruled Havertz had diverted the Spaniard’s effort in with his arm.

Related: Arsenal 2-2 Aston Villa: Premier League – live reaction

In a season where Arteta has been forced to navigate his way through a number of issues, this was another bitter pill to swallow as Arsenal attempt to end their long wait to be crowned champions again. But having seen Darwin Núñez underline the importance of having a deep squad with his crucial late interventions for Arne Slot’s side in west London, it was striking to compare the two substitute benches here.

While the only senior attacking option the hosts could call on was an out-of-sorts Raheem Sterling who came on for the last 10 minutes to little effect, Emery was able to add £20m forward Donyell Malen – who spent time in Arsenal’s academy as a teenager – to his options alongside free-scoring super-sub Jhon Durán.

Arteta has acknowledged that reinforcements are required before the end of January if his side are to stand any chance of overhauling Liverpool and it was hard to argue with that on this evidence. While they had coped well with the absence of defensive linchpin William Saliba for only the second Premier League game this season, a lapse of concentration allowed Villa back into the game after they had been second best for most of the contest.

Arsenal had made their intentions clear from the start with a barrage of early corners, although they could not find a way past Emiliano Martínez, who was one of the heroes of Villa’s victory here last year. Martínez spent eight years at Arsenal but made only 15 appearances before joining Villa in 2020. Cheered on by the visiting supporters behind his goal, the Argentina goalkeeper revels in being in the spotlight and produced a full length dive to tip away Leandro Trossard’s deflected shot.

Yet having seen their brisk start ­fizzle out, Arteta’s frustration with his side’s lack of cutting edge was ­growing until 11 minutes before half-time when Trossard picked out Martinelli, whose volley Martínez was unable to keep out, the ball marginally crossing the line.

The goal seemed to give Arsenal extra belief and they had chances to extend their lead when Trossard and Merino both failed to hit the target. In terms of effort, Arteta could not have asked for more of his players.

Emery’s response to a lacklustre first half display from his side was to withdraw Ian Maatsen for Lucas Digne. The Frenchman was immediately in the thick of the action to clear away a dangerous low cross from Myles Lewis-Skelly.

Havertz had not scored since the victory over Ipswich here just after Christmas and Arteta admitted this week that the forward had been badly affected by abusive social media messages sent to his pregnant wife. So there was an outpouring of emotion from the home supporters when the German turned home another excellent cross from Trossard to double Arsenal’s lead.

But their delight turned to worry within five minutes when Tielemens stooped to head home Digne’s perfect ball into the area. “The goal gave us freedom and belief,” said Tielemens.

Suddenly Villa sniffed a comeback and they would have been level had the Belgium midfielder’s shot not smacked off a post a minute later. Emery was booked for kicking the ball away as temperatures began to rise and he was just about to introduce Durán off the bench when Thomas Partey was caught napping at the back post and Watkins volleyed home expertly from a tight angle.

Arteta seemed stunned by how quickly things had unravelled. It would not have mattered had VAR not decided Havertz had deflected Merino’s goalbound shot in with his forearm during the dying minutes of the game but Arsenal’s uphill task is now even steeper.