There is a mutinous mood lurking very close to the surface at Arsenal – and the fractures in the relationship between manager Unai Emery, his players and the home support were exposed in the undercurrent of a poisonous atmosphere at Emirates Stadium.
Xhaka was in the wrong and Emery will need to address the situation instantly. He must hope it is not already too late because this reaction may well have lost even those who have been giving Emery’s captaincy decision the benefit of the doubt.
And then, for good measure, thousands chanted for Mesut Ozil, the gifted maverick placed in exile by Emery, not even on the bench here and seemingly persona non grata.
Ozil has also been a target for Arsenal’s fans, but his absence when the team searched for that crucial touch of inspiration late on smacks of Emery cutting off his nose to spite his face, for all the German’s failings.
It sounded like a chant to chip at Emery rather than a serious gesture of support for Ozil, who most accept has had his day if Arsenal can find anyone to take him off their hands. Emery is actually in danger of making him an unlikely martyr if this crowd reaction is anything to go by.
All in all, it was a thoroughly uncomfortable 90 minutes for Emery once the glow of those two early goals from Sokratis and David Luiz had worn off.
Luka Milivojevic’s penalty and Jordan Ayew’s header earned Palace a point, although Arsenal were understandably frustrated that a late strike from Sokratis was the latest victim of VAR. Plenty of us inside Emirates Stadium struggled to spot the apparent infringement by Calum Chambers on several viewings.
The cacophony of jeers that greeted the final whistle was not just an outpouring of VAR-induced invective, it was a reaction to yet another flawed Arsenal performance.
Quite what watching Arsenal director Josh Kroenke made of it is anyone’s guess.
There is no doubt Emery is reaching a critical phase of his reign at Arsenal.
He was hired to cure the ills of the Wenger tenure, in which the great man let things drift in the context of chasing a Premier League title and too many familiar faults reappeared on a regular basis.
Now, 10 league games into his second season and after reaching the Europa League Final last term, Emery is facing searching questions.
The odd anomaly aside, not much appears to have changed at Arsenal.
They are talented, attractive and devastating on their day. As they were under Wenger.
They are too often easy prey to committed opposition on their travels. As they were under Wenger.
They are prone to a soft centre and fallibility under pressure. As they were under Wenger.
It has all been on show this week, from the dismal defeat at Sheffield United on Monday, the struggle to victory against Vitoria Guimaraes in the Europa League on Thursday, and this home draw with Palace.
Emery’s big problem is there is no obvious personal stamp on the team, no clear strategy, no compelling evidence he is any sort of upgrade on Wenger.
Arsenal’s fragility was shown here once Palace pulled one back. Suddenly they were nervy, edgy, as were those inside the stadium, and it was no surprise when Ayew arrived unattended at the far post to restore parity.
The Gunners are still not physically or mentally strong. Palace could sense it – as could Arsenal’s fans.
And it is in this unsettled, fevered atmosphere that anger and emotion takes over.
Arsenal may be fifth in the Premier League, but there is now a four-point gap to Chelsea in fourth.
There is also a sharp contrast between the serenity and unity of Chelsea under Frank Lampard, just months into the job, and the fractious sound and fury on show here.
Arsenal’s league position may look healthy – but no-one would say all is well in this part of north London.