Arsenal let a two-goal lead slip to draw 2-2 at home with Crystal Palace as Granit Xhaka was involved in an extraordinary standoff with Emirates fans.
Sokratis Papastathopoulos and David Luiz struck within two minutes of each other to give the Gunners a commanding lead inside eight minutes.
But Palace got back in it thanks to a VAR intervention as Luka Milivojevic scored from the spot before Jordan Ayew's header in the second half rescued a point for the visitors.
VAR then came to the rescue for the Eagles again when Sokratis' strike was chalked off for a foul on Milivojevic as Palace held on for a deserved point.
And Xhaka's furious interaction with Arsenal supporters as he was substituted - appearing to tell fans to "f*** off" after being booed before tearing off his shirt and disappearing down the tunnel - is another issue Emery will have to solve in the coming days.
Mesut Ozil was once again nowhere to be seen, at least on the teamsheet, as Unai Emery rotated his squad from the 3-2 win over Vitoria on Thursday.
But it wasn't Arsenal's attackers who made an impression in the early stages. After some poor defending from the south London side, Sokratis volleyed home to break the deadlock after seven minutes.
Just 90 seconds later, the Greek's defensive partner Luiz stabbed home from another corner as Palace struggled to organise themselves, leaving Roy Hodgson furious on the touchline.
But after a slow start, they settled and found their way back into the game in bizarre circumstances. Zaha took on Calum Chambers and beat the defender with a burst of pace before going to ground. Referee Martin Atkinson gave an indirect free-kick for simulation and booked Zaha.
But a VAR check proved there was contact and Atkinson's decision was overturned. Up stepped Milivojevic and the Serbian was never going to miss.
The away side kept their momentum up in the second half and levelled when McArthur's cross found Ayew, who headed past Leno.
Arsenal thought they had won it late on when Sokratis finished delightfully from 12 yards, but after a long delay the goal was chalked off for a foul on McArthur by Chambers.
To add to the drama, Zaha nearly snatched a dramatic win for Palace only to see his shot tipped wide by Leno. The spoils were shared, but for the hosts it was most certainly a case of two points dropped.
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