That autumnal unbeaten run has long been forgotten at Arsenal. Only Burnley, Fulham and Blackpool have fallen to Unai Emery's team in the last eight games in a spell that saw the gap between them and the likes of Liverpool cruelly exposed.
And on a grey January afternoon at the London Stadium, as the mid-winter begins to bite, West Ham put them firmly back in their place.
Manuel Pellegrini's team have their own ups and downs, of course, but on an afternoon where home-grown Declan Rice shone, dominating the midfield and scoring his first goal for the club, this was definitely one of their better performances.
There was no heroic homecoming for unsettled Marko Arnautovic, who had one of those mercurial afternoons, where he offered only occasional glimpses of his class.
But there would be a crucial role for Samir Nasri, formerly of Arsenal and returning from an 18-month drugs bans. Bizarrely, footballers seem immune from the usual opprobrium reserved for drugs cheats so Nasri's return to the Premier League after an FA Cup start last weekend attracted little comment. And on the basis of this display, he will have much to offer West Ham.
For Arsenal, the lack of strategy was confined to the pitch. Mesut Ozil has belatedly discovered that £350,000 a week doesn't even get you on the bench at Arsenal these days. Three full backs and Eddie Nketiah were considered a better fit as back up options for this clash than the best-paid player in Arsenal history.
But though this wasn't the first time Unai Emery has excluded him from the squad – and both Ozil and Arsenal confirmed that he had trained all week and was available – it did feel like an even more pointed omission, coming in the January transfer window. Quite who would be willing to pick up his wages, however, remains a moot point.
MATCH FACTS, LIVE LEAGUE TABLE AND MATCH ZONE
, Zabaleta 6.5
, Diop 7
, Ogbonna 6
, Cresswell 7
, Noble 7
, Rice 8
, Antonio 7
(Obiang 82), Nasri 7
), Felipe Anderson 7
, Arnautovic 6
Adrian, Masuaku, Lucas Perez, Diangana
, Koscielny 6
, Papastathopoulos 5
, Mustafi 5
59'), Maitland-Niles 5.5
, Guendouzi 5
, Xhaka 5
59'), Kolasinac 5
, Iwobi 6.5
, Aubameyang 6
, Lacazette 5.5
Cech, Bellerin, Lichtsteiner, Monreal, Nketiah
Jonathan Moss (County Durham) 6.5
Player ratings by Adam Crafton
As worrying was that the coherence that Arsenal showed in the autumn under Emery has ebbed away. The high press and intensity is lacking. They look again like Arsene Wenger's side in the latter days: neat enough, nice in patches but without a true identity.
West Ham's intent seemed more pointed from the off, though Arnautovic was doing that thing where he does nothing and then produces one touch to convince you he is irreplaceable.
It came in the 33rd minute, where he burst into life, running in behind the Arsenal back three. The ball looked too far beyond him to be controlled, but with a stretch and one exquisite touch he brought it down and set up Nasri, who held the ball up wonderfully for Felipe Anderson to shoot from the edge of the box. The Brazilian struck it well enough but wide.
That was almost as exciting as it got in the opening half. Rice went close with a header from Anderson's corner on the stroke of half-time.
Arsenal's best chances came from a half volley from Alexandre Lacazette on nine minutes, which swerved wide and when Sead Kolasinac drove into the box with commendable intent on 23 minutes but failed to either shoot or deliver a decent cut back.
Matteo Guendouzi then struck a swerving shot with some force on 35 minutes, which curled just wide.
But West Ham were at least showing desire. And Arsenal's slackness would cost them in the opening exchanges of the second half.
They would fail to clear a Felipe Anderson corner on 48 minutes, allowing the Brazilian to drive back to the goal-line again and pull the ball back. Arsenal's defending has lately reverted to lame and here was another example, Granit Xhaka cushioning a soft header out to Nasri.
Inevitably, against his former club and on his Premier League return after his drugs ban, he delivered a moment of class, touching the ball to Rice, who in turn struck it cleanly, curling past Bernd Leno, his first goal for West Ham.
Emery soon made a change, bringing on Aaron Ramsey and Lucas Torreira and reverting to a back four. They immediately looked better, covering the space in midfield and releasing their runners, particularly Alex Iwobi, more frequently.
Kolasinac played in Aubameyang on 65 minutes and the Frenchman shot just wide. Iwobi broke free on 66 minutes and did the same. But it was the best Arsenal had looked. And it wouldn't get much better. They pushed forward without truly threatening West Ham in the final minutes.
Throughout the club, it's looking to be a long and slow rebuilding process.