Where did it all go wrong for Egan Bernal and the Ineos Grenadiers?

The dress rehearsal for Stage 15 of the Tour de France took place 35 days before the main event in the decisive third and final stage of the Tour de l'Ain – a race which in any non-Covid year would have as much bearing on the actual Tour as one of the spring classics.

Over a route which would be repeated just over a month later, the Jumbo-Visma team of Primoz Roglic laid down a marker and highlighted the cracks in the Ineos empire. Over the steep ramps of the Montée de la Selle de Fromentel and the Col de Biche, Jumbo-Visma controlled the race in a way reminiscent of Team Sky in their heyday.

And then on the final grinding climb of the Grand Colombier, the man in yellow leader's jersey pulled the trigger.

Roglic's advantage on runner-up Egan Bernal was just four seconds. 35 days later, Bernal would have settled for conceding four minutes.

Instead, the defending Tour champion toiled in the September heat and shipped 7min 20sec on the Giant of the Jura – an emphatic wake-up call, an abject humbling bordering on total emasculation, a beating from which lesser riders have never recovered.

Let's now wind back to that day in early August when Roglic's victory on the Grand Colombier saw him secure the overall victory in a largely meaningless three-day race by 18 seconds. The gap wasn't important. What stood out – to everyone – was the way in which Jumbo-Visma had dominated set against the way Ineos had struggled.

It was the first race since the restart in which both teams got their Tour teams together. Jumbo-Visma lined Roglic up with Steven Kruijswijk, Tom Dumoulin, George Bennett, Robert Gesink and Tony Martin – all of whom, bar the injured Kruijswijk, playing out their roles a month later, but with even more intensity, not to mention an a(e)rtistic flourish.

For Ineos, it was the first time in 2020 that David Brailsford fielded Bernal in the same team as Chris Froome and Geraint Thomas – the big three everyone thought would dominate the Tour.

Froome finished 12 minutes back on the Grand Colombier, Thomas a further four minutes in arrears. A fortnight later, they reconvened in the Dauphiné, but the writing was already on the wall.

Brailsford decided to jettison his duo of British former winners in favour of a selection that offered more clarity: the sole goal was a second successive win for Bernal; there was to be no distraction, no room for dining out on past glories.

How Brailsford must wish he had shown a little room for sentimentality. If Bernal could have done with an in-form Thomas or Froome on the Grand Colombier, Ineos could equally have done with a viable Plan B in the event of a Bernal implosion.

For the Dauphiné was more than the race which swayed Brailsford's mind when it came to his selection ahead of the Tour, it was the race where the first question marks over Bernal's fitness were raised after he withdrew with a back injury. It was an injury the team said was not serious – his withdrawal merely precautionary – but an injury which seems to have hampered the Colombian during the steep stuff of this Tour.

It didn't help that the two riders brought in at the eleventh hour to replace Froome and Thomas – the Russian Pavel Sivakov and the Ecuadorian Richard Carapaz – both crashed badly in the opening weekend around Nice.

Sivakov looked impressive after the restart but his injuries from that baptism of fire on his first day in the Tour knocked the stuffing out of him. Carapaz had suffered numerous crashes – none as serious as Sivakov's – and enough untimely mechanicals to think his own maiden Tour was somehow cursed. Meanwhile, another questionable selection – Costa Rica's Andrey Amador – has been largely invisible.

The Devil's Advocate would say that if you choose to send a team featuring three former Movistar riders to the Tour, then there's a good chance that the team will start to perform like, well, Movistar on the Tour…

It was the third former Movistar rider, Jonathan Castroviejo, who rode up the Grand Colombier alongside Bernal after his collapse, with Poland's Michal Kwiatkowski also present to lend moral support: the only two riders who the Colombian has been able to rely on this September. Compare that to the level of support usually reserved for Sky and Ineos riders, or the level that Roglic is getting right now at Jumbo-Visma…

Not only were Ineos and Bernal blown apart, the damage was done not by the man in yellow nor his Giro-winning deputy, not even mountain stalwarts like Bennett, Gesink or Sepp Kuss, but by the versatile Wout van Aert, a rider whose two victories in this Tour came in bunch sprints.

The day Bernal gets broken by a sprinter – albeit one of van Aert's immeasurable class – is the day you can throw your hands up and admit that the castle walls have tumbled, that the citadel has been penetrated, that the kingdom has been toppled.

Ineos are not going to win this Tour, that much we know. But now that Bernal is out of the picture – the Colombian no longer even in the top 10 – then it's hard to see how they can salvage anything from the race.

"I lost three years of my life today," a broken Bernal admitted in the immediate aftermath to Stage 15. "The back injury is no excuse. The team are going to have to reconsider objectives for this final week."

But do they have any riders who could be the answer to any such reconsideration? Not in the form they're currently displaying.

Of course, adding three years to Bernal's life would still make him four years younger than Roglic – although it would also make him five years older than Tadej Pogacar, the rider who, lest we forget, actually won Sunday's stage.

It's easy to get carried away and talk of a new era in cycling and a changing of the guard from Ineos to Jumbo-Visma. But this race still has a week to run. Roglic's lead is only 40 seconds. For all his team support and individual brilliance, he has get to get the better of his 21-year-old Tour debutant countryman who, to be fair, rides with even less support from his UAE team than Bernal currently does at Ineos.

Let's wait until we know which Slovenian rides into Paris in yellow before we make any firm conclusions about the changing of the guard.

What we can all agree on, however, is that this Ineos team is a busted flush.

Bernal will win the Tour again – just not this year, and not with the current support he has. Brailsford needs a rebuild or he risks falling even further behind Jumbo-Visma, a team that currently can't do any wrong.