In March, Tottenham, fearing possible relegation, spent big to bring in Roberto De Zerbi, who will probably never go into a negotiation with a stronger hand. There was obvious improvement and they stayed up on the final day of the season. Since then, Spurs have spent a net £175m ($234m) on improving the squad. The message seemed clear: the fiscal caution of the Daniel Levy era was over and this was a club willing to spend. Yet Spurs go into the first international break bottom of the Premier League table.

To an extent, the issue is confidence. On the opening weekend at Brentford, with a weird mishmash of a side, a team that was clearly undercooked, they were hammered 3-0 by much better-prepared opponents. That was not hugely surprising given how sensible Brentford’s transfer dealing had been and how early they had done it. More worrying was what happened the following week as Spurs, starting well before fading, lost 2-0 at home to Newcastle.

Goalless draws against Nottingham Forest and Everton seemed to have steadied the ship. Their biggest problem seemed to be a lack of confidence. They were tentative in possession, indecisive when chances did come. The two goals they managed in their 3-2 defeat to Aston Villa on Saturday mean Spurs climbed above Coventry to second-bottom of the goal-scoring charts, but they are ninth for shots. That should be reason for frustration rather than panic; the goals will come eventually.

But there are more concerning things to have come out of Saturday’s game. The lack of confidence in front of goal seems to have curdled into something worse, a more general mental degeneration. Again, they started well. The Villa keeper Zion Suzuki made a string of saves. And then just before half-time Villa scored a shambolic goal. Micky van de Ven was off the pitch receiving treatment. Andy Robertson, in preventing the ball running out for a corner, gifted possession to John McGinn. A cut-back, a scuffed shot and Johan Manzambi was unmarked in the six-yard box to score. It was a horrible goal to concede.

The second goal they conceded was just as bad. A long punt not dealt with, Nicolas Jackson bringing the ball down, Van de Ven not getting tight enough, a shot that bounced in off Antonin Kinsky’s hand. The third Villa goal was whipped brilliantly into the top corner by Emi Buendía, but he had space to line it up before James Maddison, who had been marking João Gomes, got out to him. Perhaps Maddison could have been more aggressive, and the slight turn of his back as Buendía struck his shot is never a good sign, but this was at least as much a failure of structure.

To an extent Spurs were unfortunate. Robertson might have cleared that ball for a throw-in, or at least got distance down the line, and Boubacar Kamara’s mishit cross could have gone anywhere. Jackson will not always be so deft in taking down a chest-high ball. Buendía, enormously technically gifted as he is, will not always pick out the top corner. But equally, each goal followed some sort of error: the Premier League is full of high-class players who will take advantage of any slip.

De Zerbi spoke of Spurs being “too fragile”, by which he seemed to be talking both of their physicality and mentality. They have players returning from injury. Like so many clubs, they brought in players late. Preseasons have been curtailed, perhaps inadequate.

Where the initial instinct was to be impressed by the numbers and the change of policy, doubts are now emerging about the nature of those summer signings. Is Sandro Tonali really worth £100m? Mateus Fernandes played for a relegated side. Jan Paul van Hecke wouldn’t be the first player to leave Brighton and find his level dip outside that precisely configured environment. Sávio and Omar Marmoush struggled to get into the team at Manchester City. Sávio’s finishing brought just two league goals in two seasons at City and the evidence of Saturday is that it has not improved.

The sense had been that this season couldn’t be as bad as the last two for Spurs. There is no Europe to distract them. The injury crises couldn’t be as bad again. De Zerbi has proved his worth in the Premier League before. They have spent money. And yet this is as bad as it’s ever been. Once a club of Tottenham’s stature could have dismissed this as a blip, the kind of thing that would inevitably sort itself out as the season went on. After the last two seasons, nobody can be quite that confident again.

It’s still implausible Spurs could be relegated, unlikely even that they’ll be in another fight, but those preseason thoughts of European qualification are already beginning to look bafflingly optimistic – and that will inevitably slow the rebuilding of the club.