Sean Kelly believes Chris Froome's rivals will be kicking themselves for not having done more to take the yellow jersey off his shoulders during yesterday's dramatic stage nine of the Tour de France.

Froome's Team Sky squad fell apart during the first of the five categorised climbs in the Pyrenees yesterday, leaving the race leader exposed amid a pack of predators as he had to defend himself without any support.

That the 28-year-old managed to do so without losing any time - he still leads the second-placed Alejandro Valverde by one minute 25 seconds - showed yet another side to his armoury and reinforced the impression that he is the strongest rider on the Tour.

But the vulnerabilities shown by his Sky team-mates left plenty of question marks about their overall grip on the race, which had looked so strong only 24 hours before.

"If you go back a day to stage eight on Ax 3 Domaines when Froome won so convincingly, riding away with his team so strong, people were saying, 'God, the race is over'," Kelly told Press Association Sport.

"But then yesterday within 24 hours it changed completely and you could see how vulnerable Sky were. You couldn't have foreseen that change.

"The other teams have seen Sky are breakable. But yesterday there was an opportunity for some teams to really take them on and they didn't do it. They needed to attack between the climbs to put Froome in difficulty."

Kelly described the situation Froome found himself in all alone as "scary" but was impressed with the Kenyan-born Brit's response.

"The stress can affect a rider but he handled it all," said Kelly, who is working at the Tour as a commentator for Eurosport.

"He could not have done it better. He didn't show any cracks at all."

While Froome shone, there is no question Sky have been weakened with Richie Porte losing 17 minutes to surrender second place overall, while Peter Kennaugh was involved in a scary crash and Vasili Kiryienka was eliminated after being swept up by the broom wagon.

That will create opportunities for Froome's rivals to attack again, but Kelly believes they will rue the one that got away.

"You don't get many chances in the Tour de France with the yellow jersey on his own, totally isolated," he said.

"You may get one. If you get two, you are very lucky indeed."

Kelly, who won five Tour stages during his career, was able to watch Dan Martin become the first Irishman to take a Tour victory since his uncle Stephen Roche in 1992 as the Garmin-Sharp man broke away on the final climb of the day to finish 20 seconds ahead of the group containing Froome.

Amid all the excitement surrounding the yellow jersey battle it might have been easy to overlook Martin's performance but Kelly was full of praise for the 26-year-old.

"To win yesterday's stage it had to be a really brilliant ride," he said. "To ride away on the final climb when you had (Nairo) Quintana trying to attack Froome and the likes of Valverde and (Alberto) Contador not able to do anything, it was fabulous.

"We've seen it already this year at the Volta a Catalunya and Liege-Bastogne-Liege (both won by Martin). When he gets into a winning situation he keeps his cool. You've got to have the legs but you've also got to have the head."