It wasn’t just a first big test for the Ole Gunnar Solskjaer regime, or a first defeat, but also a crucial first mis-step.
It was at half-time of Manchester United’s defeat to Paris Saint-Germain when he suffered the misfortune of losing two of his fastest players in Jesse Lingard and Anthony Martial to injury, but he didn’t respond with the sharpness you would associate with his time so far. In what had been a stodgy stop-start game, Solskjaer decided to replace them with a stodgier-style playmaker in Juan Mata, and a very stop-start player right now in Alexis Sanchez.
It had the effect of both making United even more lethargic looking, and crucially released Paris Saint-Germain from the wariness of getting caught on the break. It felt absolutely no coincidence that, already emboldened by the treatment of Angel Di Maria, the French champions suddenly felt free to go at United. It was enough. Solskjaer’s substitutions had ceded space, initiative and ultimately the game.
A football figure made famous by his adept reading of games from the sidelines just read this one wrong. Given that United’s pace had been pinning PSG back, why not bring on Romelu Lukaku - at the very least - given the ample evidence of his effectiveness out wide?
While that has come close to killing this Champions League tie, this is obviously by no means definitive about his ability to be United manager. The hierarchy are already hugely persuaded by what he’s done so far, even if this proved they shouldn't be too hasty in any decision of their own, and maybe wait until May.
In saying that, every manager will have missteps at what is by far the top level of football. Sir Alex Ferguson had many in the Champions League. Pep Guardiola more than his fair share.
There’s also the basic truth that Paris Saint-Germain are just a better team, with better players, and in better shape. They’re far closer to what European champions should look like, as Solskjaer admitted.
“This is a level up from what we've played against,” the Norwegian. “It was a big step-up.”
PSG especially showed that on going ahead, and showed all the nous and experience that is missing from United.
That also reflects a wider issue, that in turn made Solskaer’s misstep more costly than it might have been.
If this has broken the manager’s momentum, and now set an important challenge for him to positively respond to - something, to be fair, he always anticipated - it has also shown the club they must respond to their own challenges. They must bolster this squad. Jose Mourinho was by no means completely wrong on everything, even if his effect was by the end making everything worse.
This is a hugely talented squad but still a lopsided one, haphazardly put together. Little wonder the talk is of bringing in a centre-half, a right-back and more options up front in the summer. It was actually the latter that surprisingly told most of all here, especially when Lingard and Martial were forced off.
In that way, Solskjaer’s ability to read a game actually worked against him. He had been preparing for this match for so long, and had such a specific plan, only to lose two key players at the same time. He then had to react to that in a matter of minutes.
Little wonder it can go so wrong, especially against such quality. Especially against Kylian Mbappe. Things were never going to go as swimmingly as the opening unbeaten run suggested.
This will ask other questions of Solskjaer’s management, of qualities initially being so held up as making him so right for the job: the mood he engenders; the tone he sets; the sense of adventure; the resilience he grew up with at United, and now so carries.
But it will also ask questions of the squad.
With Paul Pogba now stupidly suspended, and Lingard and Martial maybe out for a while, they need to look how they reshape that attack. They may need youth graduates like Tahith Chong and Mason Greenwood on the bench.
They now need a response, for the first time.
Solskjaer’s response here was inadequate, even allowing for PSG’s superiority.
The hope is it just leads to a superior United.