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Roberto De Zerbi may have spent close to £400m by the time his Tottenham Hotspur rebuild is complete – but it took just his side's first Premier League game of the season to prove all the money in the world is no guaranteed cure for a losing mentality.

De Zerbi, by his own admission, confirmed his role was more psychologist than coach when he was given seven games to keep Spurs in the top-flight following his appointment in March. He achieved that feat, but only just as Spurs survived with victory against Everton on the final day.

The Italian has been handed vast funds for a host of new players to ensure Spurs do not suffer a repeat of the nightmare campaign. This dreadful defeat was not the start he or the Spurs power brokers envisaged.

For all the change in transfer strategy and personnel, the manner in which Spurs capitulated at the first sign of pressure as they were run ragged by Brentford provided gruesome evidence that you need more than a huge transfer fund to give a team mental strength.

De Zerbi may feel he has addressed some of the ills in a squad that has finished 17th in the Premier League two seasons in succession. However, he will have to turn psychologist once more as the new Spurs looked like the old Spurs as they were dismantled in the west London sunshine.

He pointed to a lack of physical conditioning of players who had been at the World Cup or were newcomers, but this did not excuse the lack of basics, shortage of resilience and the fact Brentford were so superior in every area.

De Zerbi told BBC Sport's Match of the Day: "Bad game. We lost and suffered the difference in the duels. It was the key of this game. We didn't fight in the right way. Maybe credit to them because it's the best quality Brentford have."

"Our physical condition was not in the right level for all players because many came later after the World Cup and there were many new players in the squad and first XI. But we have to analyse this game better because we can't play this way in this type of game."

The day started with Spurs fans bursting with optimism in one corner of The Gtech Community Stadium, welcoming their new recruits raucously. It ended with those same players applauding a large swathe of empty seats, some vacating as early as the 49th minute when Michael Kayode put The Bees 3-0 up.

It could have been even worse had the normally reliable Igor Thiago not struck the post with a penalty, but that was no consolation for Spurs or De Zerbi on what was a chastening day.

Rock superstar Jon Bon Jovi was an interested spectator at The Gtech Stadium - and Spurs gave him enough material for several albums worth of sad power ballads as they started badly and went into rapid decline.

De Zerbi gave debuts to four of his new acquisitions in Andrew Robertson, Marcos Senesi, Jan Paul van Hecke and Sandro Tonali. They will feel the only way is up because they were at rock bottom here.

None of them distinguished themselves, although neither did any others. Italian midfielder Tonali cost £100m from Newcastle United, but was utterly outshone and overpowered by Brentford's record buy Mamadou Sangare, who was the game's outstanding performer. Tonali's only memorable contribution was a first-half attempt on goal that flew horribly skywards, prompting the inevitable suggestion from Brentford supporters that Spurs had wasted their money.

Spurs coach Roberto De Zerbi in despair as his new-look side slump to a heavy defeat at Brentford on the opening day of the Premier League season. Matheus Fernades, at £85m from West Ham United, came on as a substitute, while Savinho and possibly Omar Marmoush will add strength, but it was the lack of heart and fight that will be De Zerbi's biggest concern.

From the first minute, Spurs' brave new world hauntingly resembled the old one as they cracked under the first sign of pressure, Brentford sensing their weakness as they hunted down a side they clearly felt could be exposed. And how Spurs were exposed.

Brentford should have been ahead before Keane Lewis-Potter broke the deadlock after 12 minutes, the contest effectively over when Vitaly Janelt doubled their lead before half-time.

De Zerbi cut a frustrated, animated figure as he tried to enliven Spurs, but heads were down, physical challenges lost, desperation their trademark, with not the slightest indication of any self-belief that they might recover the situation.

Conor Gallagher and Lucas Bergvall did not return after the half-time interval, although they might justifiably point out others could have accompanied them.

De Zerbi somehow needs to get into the heads of these Spurs players to give them strength and steel. That is not something that can be achieved with a wave of the chequebook.

For context, this is Spurs' first game of the Premier League season and many teams with aspiration and ambition have had nightmare starts. This, however, looked like the worrying continuation of a pattern of defeat and despair.

That pattern has cast a cloud over Spurs' recent seasons, along with De Zerbi's predecessors Ange Postecoglou, who at least won the Europa League, then Thomas Frank and – in his "blink and you'll miss it" reign – Igor Tudor.

De Zerbi added: "I am surprised for the result and performance. I knew we were not in the right condition. We can't find an excuse. I am sorry for the result and performance. We are starting a new project and we couldn't find the principle."

"Marcos Senesi, Jan Paul van Hecke and Sandro Tonali are not in the best physical condition. We knew that before the game. We have to improve on that and many other things like organisation and pressing."

More signings may be on the way, but De Zerbi said: "I don't want the excuse that the first XI was not enough to compete and get a result. Brentford's spirit on the pitch was great, it has to be the right example for us."

New faces are all very well, but this loss showed Spurs problems run deeper than fresh personnel. De Zerbi must banish the ghosts of two seasons littered with losses. And quickly. He must not change his squad. He must change a culture in which defeats like this have become commonplace.

Rock superstar Jon Bon Jovi was an interested spectator at Brentford v Spurs. Spurs make nightmare start as Brentford hit three in easy win Tonali nightmare as Sangare stars - Brentford v Spurs player ratings.