Sir Dave Brailsford hails efforts of Michal Kwiatkowski

The former world champion has put in one of the rides of his life over the past three weeks, with his contribution exceeding what was asked or expected by his team.

Kwiatkowski was included in Sky's nine-man squad with a brief to help Froome on the flat and the rolling roads, but time and again he was seen leading the Sky train high into the mountains.

"What's made him outstanding is not just the amount of work that he's done, but also the terrain that he's been able to contribute on," said Sky team principal Sir Dave Brailsford.

"He can contribute in crosswinds and the lead-out in the final on the flat. He's got the speed and the know-how. But then he was there six kilometres from the top of the Col d'Izoard as well.

"He's been the man of the match."

Kwiatkowski was dubbed as a 'vanity signing' when Sky forked out a considerable salary to land him from what was Etixx-QuickStep at the start of the 2016 season.

Illnesses and injury plagued his first season with the team as he struggled to shake off that tag, but 2017 has revealed what Sky were paying for.

He won Strade Bianche and then his first Monument, Milan-SanRemo, in March, before finishing second in the Amstel Gold Race and third in Liege-Bastogne-Liege.

That outstanding form has continued in the Tour, where the affable Pole was able to thrive in a different role.

"I always enjoy riding for someone who's got a chance to win the race," he said. "This year in the Tour de France, Team Sky were aiming for one goal, the biggest goal you can aim for, the yellow jersey. I really enjoyed supporting Chris on his way to Paris."

Far from being a vanity signing, the 27-year-old has more than proven his worth, and the team are poised to tie him down with a new three-year contract after the Tour.

It is not just his riding which has proven invaluable to Froome.

With the margins in this year's Tour close throughout, Froome could easily have lost yellow - and the race - when he suffered a broken spoke late on stage 15.

With the race fully on at the foot of the Col de Peyra Taillade, Kwiatkowski executed a swift rear wheel change for his team leader - getting him back on the road just in time to save the day.

Brailsford called Kwiatkowski Sky's "tech geek" - the guy on the bus everyone takes their gadgets to if they have a problem - so Froome could not have wished for a better team-mate to have around when he needed a mechanic.

Kwiatkowski, who finished 11th in his first Tour in 2013, was one second off winning the stage 20 time trial in Marseille on Saturday, but that is as far as his own ambitions have gone in this race.

After being used to targeting multiple goals with his former team, Kwaitkowski said he had enjoyed Sky's single-minded pursuit of yellow.

"We just focused on one goal," he said. "Every single day it was about the GC. It was not about stages or the green jersey or mountain points or going in breakaways. In my experience that's a lot of pressure.

"Compared to my last Tour de France with Quick-Step, trying to be in the break or winning stages or the team classification, I really enjoyed just helping Chris."

That enjoyment has been clear to see both to fans and his team-mates.

On the Izoard, he went so deep in guiding Froome as far up the mountain as he could that when he peeled off he stopped dead, needing to put a foot down to catch his breath before he could continue.

Yet he was all smiles when he made it back to the team bus.

"He came back pretty buoyant, enjoying himself," Brailsford said. "He's having a ball. I said, 'You're loving this, aren't you?' and he said, 'Yes, you can win without winning. I'm winning'."