When Petr Cech stood up, blew out his cheeks and glanced down at his chest having returned the ball to the centre circle for a second time, it might have been to check if he was naked.
There, in his new home in the Emirates goalmouth, wearing his new kit, an anxiety dream was unfolding.
First, he tried to run but could not get there. Next, he tried to dive but could not move.
Then, all of a sudden, in an almost entirely empty stadium, it was full-time. Arsenal had lost 2-0 to West Ham, and the man who was meant to drive this ever-brightening team on to bigger things had instead consigned them to a humiliating opening day defeat.
If the great man does go on to do great things in the Arsenal goal in the coming years, he will still never forget how it all began. Maybe, he might wonder, he should not have gone. Certainly, in the 43rd minute, he should not have come.
If you choose to rush out for a cross, you must get there. Hardly the rudimentary goalkeeping lesson a man of his stature should need. And not the sort of opportunity Cheikhou Kouyaté was likely to turn down either.
The visitors were 1-0 up, and it was fully deserved.
The second was of the kind that, had it happened in a less reputable league around the world, would have alerted the match-fixing police. In the 57th minute, Alex Oxlade-Chamberlain gave the ball to Mauro Zarate as though it were a Christmas present and by the time Cech had flopped casually to his right, it was already in the back of the net. A 25-yard embarrassment.
The 12 or so Arsenal fans who remained in the stadium by the time the triumphant West Ham players turned away from their uproarious supporters raised their arms and clapped their opposition down the tunnel - a gesture that was met with boos by the thousands streaming for the exits. It was the sort of tableau that only ever unfolds in football.
The early stages had everything most people want from a football match. Enough aggression to put two West Ham players in the book within eight minutes and enough attacking intent from both sides to jolt what could and should be a pivotal season for both sides into life.
Arsenal appeared at times still on holiday. West Ham have barely had a break. And via the quick feet and brilliant brain of Dimitri Payet they played the type of football their fans always demand. He might just be the most accomplished West Ham footballer in a decade.
There was, of course, another Ox. Almost forgotten amid the bravery, discipline and sheer verve of West Ham's performance was Reece Oxford who, at 16 years of age, became the youngest player to start for the Hammers in the English leagues (He made his debut a month ago, in a Europa League qualifier in Andorra).
When his new manager, Slaven Bilic, started for West Ham at Highbury on the opening day of the 1996 season, Oxford had not yet been born. That day, West Ham's lack of spark - as they lost 2-0 - was put down to the injury of their two new signings, Paulo Futre and Florin Raducioiu.
"Only on paper is he 16 ," Bilic said. "He is a part of this new generation. Put it this way, if Messi was in front of me I would be more fazed than Reece."
Arsenal's midfield, with the likes of Santi Cazorla, Mesut Özil and Aaron Ramsey, are able to tease their way beyond any opposing midfield in the world. Oxford was resolute. The rough in their diamond.
Then there is Angelo Ogbonna who, having played 41 league games for Juventus in the last two years, was as assured in defence as you should expect.
Thierry Henry is not alone in his view that Arsenal are still a truly world-class striker short of challenging for the title. When Alexis Sanchez is not on the pitch, the deficit appears vast.
His introduction with 20 minutes to go transformed the way the match was played, but it made no difference to the result.
There is no point in offering an assessment of what Arsenal might yet achieve on the basis of this game.
Each individual player was too far below his own standards to imagine it could continue in this way. They will improve.
But you can only lose four games if you want to win the league, or so said Sir Alex Ferguson, who managed it a few times.
There are only three of those left in the bank now, and there are sterner challenges to come.
ARSENAL: Cech, Debuchy, Mertesacker, Koscielny, Monreal, Coquelin, Cazorla, Ramsey, Ozil, Oxlade-Chamberlain, Giroud. Subs: Gibbs, Gabriel, Arteta, Ospina, Walcott (Coquelin, 58 mins), Sanchez (Debuchy, 67 mins), Chambers.
West Ham: Adrian, Tomkins, Reid, Ogbonna, Cresswell, Oxford, Noble, Kouyate, Payet, Zarate, Sakho. Subs: Randolph, Nolan (Oxford, 79 mins), Jarvis (Zarate, 63 mins), Collins, Maiga (Sakho, 90 mins), Poyet, Lanzini.
Man of the match: Dimitri Payet
Match rating: 9/10
Referee: Martin Atkinson (W Yorkshire)