Having lost their unbeaten record, Arsenal have now lost the leadership. For the first time since 18 January they do not sit on top of the Premier League. It may just be a dent to their imperious progress, but just one victory in six matches in all competitions will grate on Arsène Wenger as well as concern him.
Indeed, as with Southampton last weekend, they were probably fortunate to escape with a draw. Crystal Palace, who produced a display of belligerent defiance and belief, squandered the best chance to win when their substitute, Vassilis Lakis, ballooned over from three yards just seconds after he had constructed the home side's equaliser.
It was joyous stuff, for Palace at least. Suddenly the Premiership does not look quite so daunting for Iain Dowie and his men. Arsenal may have won just one in six (and that came from what Manchester City's Kevin Keegan described as their "third team" in the Carling Cup), but Palace have lost just one in six. It's a symmetry that no one would have predicted at the season's start. Few could blame the gloating of chairman Simon Jordan, who baited those who had written off his club. And even if they now have to face the two Uniteds, Manchester and Newcastle, as well as Liverpool, it is perhaps not the "Nightmare November" their captain Tony Popovic feared it would be.
Wenger had threatened to freshen up his team but, in the event, he omitted only Dennis Bergkamp. He may now speed up that process. Robert Pires, in particular, appears jaded and although it would be brave to rest Thierry Henry, especially after he scored his tenth goal this season, it may be necessary. Robin van Persie certainly needs his head, although he will get his chance in the midweek League Cup tie against Everton.
It was Chelsea's defeat of those same opponents which saw them usurp Arsenal, and they have now turned a five-point deficit into a two-point lead. That's some swing, and one completed in double-quick time. Not that Arsenal started as if they were concerned. Early shots from Henry and Jose Antonio Reyes appeared to settle them and startle Palace. Soon they were constructing mesmeric passing movements of 10, 20 and, once, almost 30 interchanges. Each had the virtue of forward movement.
Palace appeared catatonic, not only surrendering territory but also possession, when meagre rations of it were allowed to them. Cesc Fabregas fed Henry and, instinctively, the striker drove his shot in from an acute angle. It cleared the crossbar. From a free-kick Gonzalo Sorondo stood rooted as his team-mates charged out. The debutant defender - in for the injured Fitz Hall although soon to depart himself with a damaged hamstring - was left with two to mark. Fortunately he put enough pressure on Patrick Vieira for his header to screw wide while, later, Reyes struck Pires' cut-back off a defender's chest.
But Arsenal had not pressed their advantage. In Michael Hughes, Palace possessed at least one player who was not fazed. Hughes epitomises the work ethic inculcated by Dowie, but it wasn't until Jens Lehmann's lazy clearance struck the effervescent Andy Johnson that belief truly returned. The moment disrupted Arsenal and, despite shots from Kolo Touré, and a dangerous cross from Henry which evaded Fredrik Ljungberg, their synchronicity was missing.
After the break and still Arsenal toiled. On a break-out the pace of Johnson embarrassed Pascal Cygan while Hughes snapped at Vieira. Twice he whisked the ball away. The frustration showed, with a wild slash at a shot from Ashley Cole 30 yards out, while Palace drew cheers from their fans as they assembled their own passing moves.
Arsenal treated it an insult and on 63 minutes they took the lead. It was an incisive strike. Ljungberg pushed forward down the right and exchanged passes with Fabregas. As he collected the return he eschewed the chance to shoot and drove the ball low into the six-yard area, where Henry clipped it in for only the second of his last 19 Premiership goals to come away from Highbury. Incredibly, Palace found an immediate response. It was a goal as finely constructed as Arsenal's, with Lakis centering low for Aki Riihilahti, at full stretch, to bundle the ball joyfully into the net.
What was impressive was the number of players Palace committed forward, and they did so again from the re-start with Touré blocking Lakis's shot. Wenger made changes and threw on both his Dutch substitutes but although Arsenal tried to slow the pace, and Van Persie twice came close, Palace would not allow them. They poured forward with Johnson the outlet. Twice he tore down the right. Both times his crosses were cleared and with an increasing - and unusual - desperation.