He went down without contact in the 30th minute, in Dallas, on the night of 14 July, kicked the ball away in something between frustration and diagnosis, and lowered himself to the turf. Team-mates say he told them his back was gone. France went on to lose the World Cup semi-final 2-0 to Spain, Maxence Lacroix on in his place, and William Saliba flew home to London to find out exactly how gone.

The club statement, when it came, was the sort of document written by people choosing every word with a lawyer in the next room. Saliba had suffered a back injury "which will require a period of rehabilitation." Surgery was "not recommended." He would begin "a managed recovery programme" and be "out of action for an extended period." Nobody at Arsenal will put a number on that period in public, though reporting elsewhere has floated five months, which would take him past Christmas and into the thick of it.

What that vagueness obscures is a fact buried three paragraphs into the same reporting: Saliba had been carrying this injury since March, playing through it to help win Arsenal's first league title in twenty-two years and to reach a Champions League final, then playing through it again for France across a World Cup campaign that ran him out for four starts before his back finally said no. Fifty appearances for club last season. Add the international caps and you get a number nobody at London Colney is proud of, because the pride was in the fact he never seemed to need a rest.

Here is the honest case for calm, and it deserves to be made properly rather than waved off. Ben White is back in training after the knee injury he picked up against West Ham in May, the one that cost him the Champions League final. Cristhian Mosquera had a genuinely good first season in England, comfortable enough alongside Gabriel in the stretches Saliba missed that nobody much remarked on it. Riccardo Calafiori can play there. Arteta has bodies. A manager who won the league with this squad has earned the benefit of the doubt on how he uses it, and it would be premature, before a ball is kicked in anger, to declare a crisis on the strength of a training-ground press release.

But look at what those bodies actually are. White is not a fit centre-back returning to form, he is a man coming back from his own operating table. Jurrien Timber, the fourth name usually mentioned, is still working through the groin injury that kept him out of the World Cup entirely and says only that he is "hopefully back soon," which is the sort of sentence players say when they don't know either. Mosquera is promising and genuinely inexperienced at this level, twenty-odd Premier League appearances into a career that has not yet included a title run without Saliba alongside him for most of it. The depth chart Arteta can point to in July is largely a list of men in various stages of their own rehabilitation, not a settled second option waiting for its chance.

The memory of last season, already, is that Arsenal's defence was simply excellent — Gabriel and Saliba, a wall, the kind of partnership pundits reach for when they want a compliment that sounds structural rather than lucky. The record says something narrower and more precarious: it was excellent because one specific pairing played almost continuously, through pain in Saliba's case, because the alternative was never seriously tested. Every winning back line eventually gets remembered as a system. Most of them were actually a pair of very good, very tired men who didn't get injured until the trophy was already in the cabinet.

None of this is new to English football, and it is worth saying plainly that Arsenal are not the first champions to discover their defence was one body short of a plan. Settled back fours win titles precisely because they are settled — continuity is the point — and the same continuity is what makes their absence, when it finally arrives, look like a crisis rather than routine squad rotation. The trouble isn't that Arsenal relied on Saliba. Every good side relies on somebody. The trouble is that reliance was never stress-tested, because he never let it be, and now the test is arriving at the worst possible moment to sit it.

Arsenal play Manchester City in the Community Shield on 16 August and open the league defence against Coventry City at the Emirates on 22 August, five days later, both games almost certainly without their first-choice centre-back. Arteta has three weeks of pre-season left to decide whether Mosquera starts both, whether White is risked sooner than his knee would like, or whether the transfer market gets one more phone call before the window shuts. Whichever he chooses will tell you more about the actual state of this squad than anything written about it last May.