Captain Granit Xhaka appeared to swear at Arsenal supporters after he was substituted during their Premier League draw against Crystal Palace as they allowed a two-goal lead to slip.
The incident and result will see pressure grow on both Xhaka and head coach Unai Emery, who has backed the 27-year-old amid fierce fan criticism.
Early goals from defensive pairing Sokratis Papastathopoulos and David Luiz inside 106 seconds proved insufficient to earn three points as Palace fought back to draw 2-2.
The video assistant referee overturned a decision to book Wilfried Zaha for diving and instead gave the visitors a penalty, which was despatched by Luka Milivojevic, before Jordan Ayew's fourth goal in eight games secured a share of the spoils.
There was further VAR drama late on as Sokratis was denied a late winner.
The result – and another poor performance from Arsenal – will be forgotten long before the incident with Xhaka as the Swiss midfielder plodded off in the 61st minute.
A decisive figure among fans, the fact he was being withdrawn was initially greeted by large cheers, which soon turned to jeers as he took his time to leave the pitch despite the score being level.
He reacted by waving his arms, cupping his ears and seemingly mouthing "F*** off" twice as he pushed away a handshake from Emery, took off his shirt and headed straight down the tunnel.
The day had started so well for under-fire Emery as Wayne Hennessey came off his line but got nowhere near Nicolas Pepe's corner – with Gary Cahill unable to clear the box with a header as Xhaka nodded down for Sokratis to fire home.
It got even better for the hosts as they doubled their lead from another Pepe corner less than two minutes later, Alexandre Lacazette flicking on for Luiz to poke home from point-blank range.
Despite their early dominance, Arsenal let Palace back into the game as VAR overturned referee Martin Atkinson's decision to book Zaha for diving, instead awarding Roy Hodgson's men a penalty for a foul by Calum Chambers.
Palace captain Milivojevic stepped up to calmly send Bernd Leno the wrong way and half the arrears just after the half-hour mark.
A lull in proceedings followed, with Pepe bending a strike just wide as Arsenal looked to regain their two-goal advantage before the interval – although Leno had to be on guard to push away a Patrick Van Aarnholt shot on the stroke of half-time.
On the field, the change seemed to pay dividends in terms of turning the tide in favour of Arsenal, Lacazette forcing a save from Hennessey as they pushed for the lead.
They thought they had snatched a win as Sokratis rifled home after a Pepe corner had not been cleared but, after a lengthy VAR check, the goal was chalked off for a foul by Chambers moments earlier.
Hennessey made a good late save to keep out Luiz's shot while Zaha went close at the other end as Palace finished the game well, although the fall-out for Emery and Xhaka will no doubt be of wider interest.
