His is likely to have been the only clear head in Kirklees come yesterday morning.
That much was obvious from the moment Lee Mason blew the final whistle to signal that the Terriers had beaten Manchester United for the first time since 1952.
All around the John Smith’s Stadium, the elation at beating one of football’s true super-powers saw fans embrace, gyrate and salute their heroes during a celebratory lap of honour that culminated in the now familiar sight of the team linking arms and raising their hands in triumph to huge cheers. A few damp eyes could also be spotted, as the magnitude of what their team had just achieved began to sink in.
Huddersfield, or ‘Little Huddersfield’ as Wagner insists on calling Yorkshire’s sole representative in the top flight, had just achieved the unthinkable and it was clear the party was going to stretch long into the night.
Wagner may have abstained from toasting such a famous victory with a beer or three but he was well aware just what getting the better of a club who spent £150m on just three players last summer meant to the town.
“I live in Huddersfield so I know a little bit, maybe not 100 per cent, about how huge this result is for the town, for the supporters, for the chairman, for the board and for everyone who supports this football club,” said the German, who will celebrate his second anniversary at the helm early next month.
“I am totally aware that this is a very special moment. A huge result for little Huddersfield Town. I am happy and proud.”
For a club who had last visited the town 46 years ago, United looked surprisingly reluctant to embrace their new surrounds.
Not only did Jose Mourinho and his players opt to stay overnight in Manchester rather than on this side of the Pennines but their body language betrayed a desire to be anywhere but the John Smith’s Stadium.
This could have been something to do with the weather, which even before the heavens opened in the second half had been blustery and inhospitable. Or it might have been the mistaken belief that all United had to do to collect the three points was simply turn up.
If the latter, such a notion was quickly dispelled by both the ferocity of Town’s early play and a raucous atmosphere that was more akin to a big cup tie than a Premier League encounter.
On the pitch, the tone for the hosts was set early by a crunching tackle from Tommy Smith that upset Anthony Martial sufficiently for the French striker to aim a petulant kick at the Terriers captain.
Moments later, Smith and Martial had to be separated by team-mates and the pair both earned a booking for their troubles. Soon after, Christopher Schindler became the third name to be written in Mason’s notebook after unceremoniously scything down Jesse Lingard. The message was clear. Huddersfield were up for the scrap.
Roared on by a crowd that was announced as almost 300 above the Stadium’s official capacity, Town made life difficult for their illustrious visitors.
Not just in terms of the pressing game that Wagner brought with him from Germany when succeeding Chris Powell but also via some incisive attacking play of their own.
Aaron Mooy being pushed forward into a more advanced role helped, as did Tom Ince’s switch from No 10 to a position on the flank that is much more suited to his talents.
With Jonathan Hogg and Danny Williams providing an impenetrable defensive barrier behind the attacking trio of Mooy, Ince and Elias Kachunga, it meant Huddersfield possessed a balance in midfield that had been lacking during much of the recent six-game winless run.
The opening goal came in the 28th minute and owed everything to Mooy’s tenacity. A heavy touch from Juan Mata inside the centre circle was all the invitation the Australian required.
Possession duly claimed, Mooy darted forward before slipping a pass to Ince. He then made light work of beating Victor Lindelof before firing a shot that David De Gea could only parry to Mooy and he did the rest.
A 434-minute goal drought had ended and, just like the proverbial London bus that Mourinho had parked at Anfield the previous weekend, a second one arrived just five minutes later.
Jonas Lossl, so culpable in the defeat at Swansea a week earlier, was the creator with a raking clearance that was horribly misjudged by Lindelof. Laurent Depoitre pounced, touching the ball past De Gea before rolling it into the empty net.
Mourinho’s response during the interval was to bring Marcus Rashford and Henrikh Mkhitaryan off the bench but it took until the 76th minute for United to bring a save from Lossl, who got down smartly to block Ander Herrera’s flicked header.
Two minutes later, Rashford headed the visitors back into the game but Huddersfield would not be denied a victory that had been so long in coming that Queen Elizabeth II had only been on the throne for a month when the Red Devils had last been humbled in the town.
That season still saw the title head to Old Trafford as Town went down. On the evidence of Saturday, a repeat of either seems unlikely.