Sir Dave Brailsford admitted the Ineos Grenadiers need to go back to the drawing board as they suffered another frustrating day at the Tour de France, with Lennard Kamna beating Richard Carapaz to stage victory in Villard-de-Lans.

Carapaz was one of three Ineos riders to join a powerful breakaway on the 164km stage 16 from La Tour-du-Pin, looking to salvage something from the race after Egan Bernal's title defence collapsed on the Grand Colombier on Sunday, but his attacks fell short as Kamna accelerated away in the last 20km.

And Bernal's woes were again illustrated as he could not stay with the main contenders, riding home in a grupetto well after Kamna's stage celebrations had wrapped up, tumbling further down the general classification to sit 16th, some 19 minutes behind Primoz Roglic in yellow.

Speaking for the first time since Sunday's collapse, Brailsford told reporters his team must now go away and have a re-think, having not been able to match Roglic's powerful Jumbo-Visma squad this year.

"Have we got to go back to the drawing board? Totally — and that's quite exciting in some respects," Brailsford said. "We've got to put together a team and a coaching staff that can deliver and try and win the race again."

Bernal's struggles again raised questions over Brailsford's decision to leave both Geraint Thomas and Chris Froome out of his Tour squad – especially after Thomas finished second overall at Italian stage race Tirreno-Adriatico on Monday – but Brailsford dismissed them.

"I don't gamble," he said, pointing to both riders' lack of form immediately before the Tour.

"People are entitled to their opinions, but I didn't gamble with selection. They were big decisions. Sometimes they work, sometimes they don't. I'm sure that people have a lot to say but they're not privy to the facts that I've got.

"It was a good decision, regardless of what anybody else may think."

Tuesday's stage was always expected to go to a breakaway, with Ineos sending Carapaz, Andrey Amador and Pavel Sivakov up the road to seek a consolation stage win.

A 23-strong group broke up on the climb of the Montee de Saint-Nizier-du-Moucherotte around 20km from the line. Carapaz attacked but Kamna followed and then rode clear on the descent and valley road before the short ramp to the finish.

It was a first career Grand Tour stage win for the 24-year-old, who was second to Dani Martinez on stage 13 last week.

"It's a big, big, big relief for the team and for me," the Bora-Hansgrohe rider said. "I can almost not imagine it. The step I made this year is huge and I'm so pleased to win today."

Nicolas Roche, whose father Stephen took the yellow jersey in Villard-de-Lans back in 1987, was also in the break and came home in eighth place on the stage.

"You start the stage with the dream of winning another stage in the Tour de France but also you cannot be too greedy, you're competing against some of the best riders on the planet," the Irishman said.

"Sometimes it works, sometimes not, but Lenny today showed he was the strongest on the climb."

The main group of contenders came home together some 17 minutes later, with second-placed Tadej Pogacar on the wheel of Roglic to maintain the 40-second gap between them.

Rigoberto Uran remains third ahead of fellow Colombian Miguel Angel Lopez, with Adam Yates in fifth before Wednesday's stage 17 from Grenoble to the Col de la Loze above Meribel which is expected to prove more selective.

"I think it is the queen stage of this year's Tour," Roglic said. "The highest point, it's just crazy hard the last 5km or so, so it will be a fight for every second.

"Hopefully we have a good day with the team, I have good legs, and definitely we will do our best."