Team Sky teetered on the verge of disaster on Sunday as Chris Froome held onto the lead but his team-mates suffered a collective loss of strength that saw Richie Porte plummet out of overall contention and climbing specialist Vasil Kiryienka eliminated from the race completely after he finished outside the time limit. Afterwards Froome admitted: “It was one of the hardest days of my life on the bike.”

Sunday was supposed to be a stage where Sky were going to play a defensive game, with their rivals intimidated after Saturday’s devastating ride into the yellow jersey for Froome and second overall for Porte.

Instead, Spanish squad Movistar ripped up the script completely, attacking after the first of five major Pyrenean climbs and isolating Froome from his team-mates for almost the entire stage in a front group of some 60 riders. While Movistar’s Alejandro Valverde has now moved into second overall, it was a very worrying day for Froome, who could have come under sustained attack. Come Paris his rivals may well be ruing stage nine as a rare, glaringly obvious, chance wasted.

“It was a massive opportunity [missed] for the likes of Movistar and Saxo-Tinkoff [Valverde and Alberto Contador’s team, both amply represented in the front group] commented Ireland’s Dan Martin, the stage winner into Bagneres-de-Bigorre after the Garmin-Sharp rider broke away with Jakob Fuglsang on the final climb of La Hourquette d’Ancizan. “We saw a weakened Sky, Chris was really isolated, they waited to attack him on the climbs and that’s the worse time possible to try and do that.”

Valverde said: “We dismembered Sky, we had him [Froome] up against the ropes, and we didn’t finish him off. In any case, we did some damage to his team.”

Froome conceded: “It was one of the hardest days of my life on the bike. It was a very difficult position, I’m happy I came through the stage and haven’t lost time on my rivals.”

Losing Porte from second overall, he admitted, was a major strategic loss for Sky because “having him there was a great boost. We could have the others under pressure. It leaves us a little more exposed.”

Porte, who lost 18 minutes, praised his rivals. “Full credit to Valverde for attacking, it takes a fair set of swingers to do that,” he said. “Today was the probably the worst day I’ve had on the bike all season.”

However, Porte denied that there was any collective illness plaguing Sky. “There’s nothing going on, I think the peloton kicked our arses and that’s all there is to it.”

Sky’s first bad omen of the day on a day when they looked at their weakest in the Tour since 2011 and plunged from second overall in the teams classification to 12th came before the first climb of the day, when Mancunian Pete Kennaugh got edged off the road by a rival and went flying into a ravine.

Kennaugh, so strong on Saturday’s collective climbing tour de force by Sky, clambered his way gingerly back onto the road and continued with nothing worse than scratches and abrasions. But while Porte disappeared from the front group and even with Kennaugh’s support could not regain contact, Froome – just 24 hours after taking the race by the scruff of its neck – looked desperately vulnerable.

On the final climb, Nairo Quintana, Movistar’s co-leader, launched no less than four attacks – but they had virtually no impact. A long acceleration by Saxo-Tinkoff close to the summit shed a few more riders out the back, but as the front group of favourites then tore down to Bagneres-de-Bigorre and a welcome rest day today, the what-might-have-beens and what-ifs were already beginning to circulate in the Tour’s press room.

“We’re not here to make Froome lose, we’re here to win with Alberto,” Saxo-Tinkoff’s team director, Philippe Mauduit, said later.

Yet ultimately Martin was the only rider to score a lasting success. “We wanted to make the race exciting, as opposed to last year’s procession to Paris,” the Birmingham-born rider said, referring to the relative tedium – for non-Sky fans – imposed by the British team’s stranglehold on the race last year.

Froome himself said he had been “definitely prepared for pressure on the final climb, I was prepared for more attacks and I was glad there weren’t.” Asked if he was worried about the Alps in the final week, he added: “It doesn’t help to worry, we’re here with whoever we’ve got and we’ve got to make the best of it.”

However, the next big challenge for Froome will be individual, not collective, in Wednesday’s time trial. Should he gain more time on the rest of the field there – as seems likely, given he finished second behind Sir Bradley Wiggins in both time trials in last year’s Tour, as well as bronze in the equivalent Olympic event – Sky’s vulnerability yesterday may well be quickly forgotten.

“If anything was shown today, it was that there are a lot more tactics to bike racing than going uphill fast and time trialling fast,” Froome reasoned. But as yet, while his team suffered badly on Sunday, his superiority in either field has yet to be challenged.

Race details: Tour de France 2013

Leading final positions after Stage 8 (Castres - Ax 3 Domaines, 195km):

1 C Froome (GB) Sky Procycling 5hrs 03mins 18secs,
2 R Porte (Aus) Sky Procycling at 0.51,
3 A Valverde Belmonte (Sp) Movistar Team at 1.08,
4 B Mollema (Neth) Belkin Pro Cycling Team at 1.10,
5 L Ten Dam (Neth) Belkin Pro Cycling Team at 1.16,
6 M N Ituralde (Sp) Euskaltel-Euskadi at 1.34,
7 R Kreuziger (Cz Rep) Team Saxo-Tinkoff at 1.45,
8 A Contador Velasco (Sp) Team Saxo-Tinkoff at same time,
Selected Others:
53 P Kennaugh (GB) Sky Procycling at 11mins 09secs,
85 D Millar (GB) Garmin-Sharp at 23.12,
171 Ian Stannard (GB) Sky Procycling at 31.15,
173 M Cavendish (GB) Omega Pharma-Quick Step at same time,
180 G Thomas (GB) Sky Procycling at same time.

Stage 9 (Saint-Girons - Bagneres-de-Bigorre, 168.5km):

1 D Martin (Rep Ire) Garmin-Sharp 4hrs 43mins 03secs,
2 J Fuglsang (Den) Astana Pro Team at same time,
3 M Kwiatkowski (Pol) Omega Pharma-Quick Step at 0.20,
4 D M Fernandez (Sp) Katusha at same time,
5 J Rodriguez Oliver (Sp) Katusha at same time,
6 Cadel Evans (Aus) BMC Racing Team at same time,
7 W Poels (Neth) Vacansoleil-DCM Pro Cycling Team at same time,
8 B Mollema (Neth) Belkin Pro Cycling Team at same time,
9 D Navarro Garcia (Sp) Cofidis, Solutions Credits at same time,
10 M Monfort (Bel) RadioShack Leopard at same time.
11 A Valverde Belmonte (Sp) Movistar Team at same time,
12 A Schleck (Lux) RadioShack Leopard at same time,
13 A Contador Velasco (Sp) Team Saxo-Tinkoff at same time,
14 C Froome (GB) Sky Procycling at same time,
15 R Kreuziger (Cz Rep) Team Saxo-Tinkoff at same time,
16 M Nieve Ituralde (Sp) Euskaltel-Euskadi at same time,
17 L Ten Dam (Neth) Belkin Pro Cycling Team at same time,
18 J-C Peraud (Fr) AG2R La Mondiale at same time,
19 N Alexander Quintana Rojas (Col) Movistar Team at same time,
20 R Alberto Faria Da Costa (Portugal) Movistar Team at same time.
Selected Others:
101 P Kennaugh (GB) Sky Procycling at 22mins 43secs,
102 G Thomas (GB) Sky Procycling at same time,
139 I Stannard (GB) Sky Procycling at 26.20,
141 M Cavendish (GB) Omega Pharma-Quick Step at same time,
163 D Millar (GB) Garmin-Sharp at same time

General classification:

1 C Froome (GB) Sky Procycling 36hrs 59mins 18secs,
2 A Valverde Belmonte (Sp) Movistar Team at 1.25,
3 B Mollema (Neth) Belkin Pro Cycling Team at 1.44,
4 L Ten Dam (Neth) Belkin Pro Cycling Team at 1.50,
5 R Kreuziger (Cz Rep) Team Saxo-Tinkoff at 1.51,
6 A Contador Velasco (Sp) Team Saxo-Tinkoff at same time,
7 N Alexander Quintana Rojas (Col) Movistar Team at 2.02,
8 D Martin (Rep Ire) Garmin-Sharp at 2.28,
9 J Rodriguez Oliver (Sp) Katusha at 2.31,
10 R Alberto Faria Da Costa (Portugal) Movistar Team at 2.45,
11 M Nieve Ituralde (Sp) Euskaltel-Euskadi at 2.55,
12 J Fuglsang (Den) Astana Pro Team at 3.07,
13 M Kwiatkowski (Pol) Omega Pharma-Quick Step at 3.25,
14 J-C Peraud (Fr) AG2R La Mondiale at 3.29,
15 A Schleck (Lux) RadioShack Leopard at 4.00,
16 C Evans (Aus) BMC Racing Team at 4.36,
17 D Moreno Fernandez (Sp) Katusha at same time,
18 M Rogers (Aus) Team Saxo-Tinkoff at 6.14,
19 I Anton Hernandez (Sp) Euskaltel-Euskadi at 6.40,
20 R Bardet (Fr) AG2R La Mondiale at 7.09.
Selected Others:
70 P Kennaugh (GB) Sky Procycling at 49mins 24secs,
97 D Millar (GB) Garmin-Sharp at 1hr 06mins 11secs,
148 M Cavendish (GB) Omega Pharma-Quick Step at 1.38.50,
166 I Stannard (GB) Sky Procycling at 1.48.16,
174 G Thomas (GB) Sky Procycling at 1.51.26