The mountainous 180.5 kilometer stage from Villadiego to Los Machucos / Monumento Vaca Pasiega started with the usual mix of various riders attacking to form breakaway groups, while general classification riders sent their teams to the front of the peloton to chase down unwanted breakaway participants, who could risk endangering their positions in the overall rankings of this year's Vuelta a España.

While Team Sky took control at the front of the main peloton group featuring all general classification contenders, a six-man breakaway group formed after 27 kilometers and featured Davide Villella (Cannondale-Drapac), Julian Alaphilippe (Quick-Step Floors), Alessandro De Marchi (BMC Racing Team), Christopher Juul Jensen (Orica-Scott), Dani Moreno (Movistar Team) and Stefan Denifl (Aqua Blue Sport).

The front group saw their lead over the peloton peak when it reached 09:10 minutes after 66 kilometers.

Other teams, including Miguel Angel Lopez' Astana team and Rafal Majka's Team Bora-Hansgrohe, joined Team Sky in the chase and 100 kilometers from the finish the lead had been reduced to six minutes.

With 70 kilometers to go, the riders were contesting a technical descent under cold, rainy and foggy conditions. Narrow roads stretched out the breakaway group and since the main peloton, with camera motorcycles finding it difficult to follow the action.

In a fierce downslope attack following the Portillo de Lunada climb, Vincenzo Nibali (Bahrain-Merida) and Miguel Angel Lopez (Team Astana) attacked from the main group of general classification contenders, hoping to shake up the peloton and distance competitors before the final two climbs of the day. Speeds up to 95 km/h were measured. Nibali looked determined to win today's tough stage.

The GC riders, however, regrouped and a stretched-out main peloton group led by the Bahrain-Merida team was chasing the breakaway riders with 50 km to go. By then the front group had a 02:43 minute lead over the main group, but Villela had been dropped from the front group and was chasing in between groups in solo fashion, hoping to be able to secure more points for the mountains qualification. Majka and other riders had been dropped from the GC group.

With 33 kilometers left of the battle, Team Orica-Scott was leading the peloton for their leaders Esteban Chaves and brothers Yates. Astana took to the front as well and the lead was reduced to 02:26 minutes as the front group approached the penultimate climb of the day - the category 1 Puerto de Alisas. By then the Majka group had merged with the GC group.

With 22.9 kilometers to go, the Orica-Scott duo Esteban Chaves and Adam Yates attacked from the main peloton in pursuit of a stage victory and hoping to advance in the general classification following Chaves' disappointing performance in yesterday's individual time trial, which was won by Froome.

Other riders attacked while Team Sky set a high pace on the ascent to discourage further general classification dreamers from contemplating attacks on the remaining 2.8 kilometers of the climb. Joining the Orica-Scott duo were David De La Cruz (Quick-Step Floors), Antonio Pedrero (Movistar Team), Jarlinson Pantano (Trek-Segafredo), Antonio Nibali (Bahrain-Merida) and Pello Bilbao (Astana). The Sky team, however, was immediately behind and the riders were caught.

Denifl was first to reach the top of the mountain, with Moreno and De Marchi following his example.

Wider roads dominated the descent from Puerto de Alisas and roads were less technical and wet than earlier in the stage. The riders, however, were approaching the final climb of the stage, the Alto de Los Machucos - a mountain feared by even the biggest stars in professional cycling.

Team Sky led the main peloton closely marked by Bahrain-Merida and Team Cannondale-Drapac in support of Michael Woods. Meanwhile, Jack Haig and Magnus Cort Nielsen attacked and formed a strong duo effectively chasing the breakaway quartet. Cort Nielsen led Haig for long before falling back to the peloton, thereby leaving Haig chasing alone, which proved difficult.

5.8 kilometer from the finish Alberto Contador attacked for Team Trek-Segafredo and Lopez joined him. By then the leaders were 01:12 ahead.

While Contador and Lopez carried on their attack a multitude of other general classification contenders were chasing, but Froome appeared to be riding on fumes, unable to follow, but supported by a strong and loyal Sky team.

With Lopez unable to follow, Contador showed great form and initiative and was joined by De Marchi in chasing front rider Denifl, who had attacked solo from the breakaway group, eager to show his ability to repeat his successful riding from this year's Tour of Austria - a race he won.

Froome proved isolated and unable to follow a eight-man group of virtually all other top general classification contenders (Majka, Woods, Nibali, Steven Kruijswijk (Lotto NL-Jumbo) etc.), except Contador further up the road, 47 seconds down on Denifl with 2.7 kilometers to go.

Denifl fought hard for his home country Austria and his Aqua Blue Sport. Contador was delivering a strong and powerful performance too, eager to take a remarkable stage victory in the last race of his professional cycling career. 1.6 kilometers from the top of the mountain Contador was 0:32 minutes behind Denifl. Froome was suffering behind with only one teammate to support him in the final two kilometers.

The finish line ever closer, Denifl carried on his mission. He crossed the finish line first in solo fashion and thereby won the first stage victory for his wild card team in a grand tour. Contador arrived 28 seconds later and was since followed by Lopez, Nibali, Ilnur Zakarin (Katusha) and Majka.

Woods showed impressive form and finished the stage in 7th position for his Cannondale-Drapac team. Froome, on the other hand, delivered a lackluster performance unworthy of a Tour de France or Vuelta a España champion and was saved by his loyal teammates. Mikel Nieve assisted him across the finish line 01:46 minutes after stage winner Denifl.

"This was a typical Vuelta summit finish. I don't think anyone really enjoys gradients over 25 percent, but that's just how it is," Froome explained.

"I think I paid a little bit for yesterday's effort. I'm not really concerned (about the Angliru). Of course it's a really tough stage and probably the toughest climb of this year's Vuelta. There's still a big battle for the GC but we'll take it one stage at a time."

Denifl dedicated his stage win to his girlfriend and newborn son Xaver.

"I can't believe it. I had super, super legs today. I was waiting the whole Vuelta for this day. I paced myself the whole Vuelta, and today I went all in. It's just amazing. For me team, Aqua Blue we're in our first Grand Tour here, and winning a stage ... I'm over the moon," Denifl told Roadcycling.com.

"When I felt my legs today I was like, Oh my God, These legs are super good. So I just kept on pushing. The stage profile was perfect for me with some flats parts useful for recovery in between climbs. Now I've won a stage in the Vuelta and it's the best day in my cycling life."

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2017 Vuelta a Espana - Stage 17 results:
1    Stefan Denifl (Aut) Aqua Blue Sport       04:48:52
2    Alberto Contador Velasco (Spa) Trek-Segafredo    0:00:28    
3    Miguel Angel Lopez (Col) Astana Pro Team    0:01:04    
4    Vincenzo Nibali (Ita) Bahrain-Merida         
5    Ilnur Zakarin (Rus) Katusha-Alpecin         
6    Rafal Majka (Pol) Bora-Hansgrohe         
7    Michael Woods (Can) Team Cannondale-Drapac    0:01:13    
8    Daniel Moreno Fernandez (Spa) Movistar Team    0:01:17    
9    Wilco Kelderman (Ned) Team Sunweb    0:01:19    
10    David de la Cruz (Spa) Quick-Step Floors    0:01:42
11    Steven Kruijswijk (Ned) Team LottoNL-Jumbo         
12    Jack Haig (Aus) Orica-Scott         
13    Mikel Nieve Ituralde (Spa) Team Sky    0:01:46    
14    Christopher Froome (GBr) Team Sky         
15    Wout Poels (Ned) Team Sky    0:01:53    
16    Julian Alaphilippe (Fra) Quick-Step Floors    0:02:01    
17    Fabio Aru (Ita) Astana Pro Team    0:02:04    
18    Pello Bilbao (Spa) Astana Pro Team         
19    Louis Meintjes (RSA) UAE Team Emirates    0:02:05    
20    Romain Bardet (Fra) AG2R La Mondiale    0:02:14    
21    Sergio Pardilla Bellon (Spa) Caja Rural-Seguros RGA    0:02:16    
22    Nicolas Roche (Irl) BMC Racing Team    0:02:32    
23    Antonio Pedrero (Spa) Movistar Team    0:02:55    
24    Tejay van Garderen (USA) BMC Racing Team         
25    Aldemar Reyes (Col) Manzana Postobon    0:03:06

2017 Vuelta a Espana - General classification following stage 17:
1    Christopher Froome (GBr) Team Sky Pro Cycling       67:44:03
2    Vincenzo Nibali (Ita) Bahrain-Merida    0:01:16    
3    Wilco Kelderman (Ned) Team Sunweb    0:02:13    
4    Ilnur Zakarin (Rus) Katusha-Alpecin    0:02:25    
5    Alberto Contador Velasco (Spa) Trek-Segafredo    0:03:34    
6    Miguel Angel Lopez (Col) Astana Pro Team    0:04:39    
7    Michael Woods (Can) Team Cannondale-Drapac    0:06:33    
8    Wout Poels (Ned) Team Sky Pro Cycling    0:06:40    
9    Fabio Aru (Ita) Astana Pro Team    0:06:45    
10    David de la Cruz (Spa) Quick-Step Floors    0:10:10
11    Steven Kruijswijk (Ned) Team LottoNL-Jumbo    0:10:13    
12    Johan Esteban Chaves Rubio (Col) Orica-Scott    0:10:46    
13    Tejay van Garderen (USA) BMC Racing Team    0:11:20    
14    Louis Meintjes (RSA) UAE Team Emirates    0:13:03    
15    Mikel Nieve Ituralde (Spa) Team Sky    0:23:20    
16    Sergio Pardilla Bellon (Spa) Caja Rural-Seguros RGA    0:24:28    
17    Nicolas Roche (Irl) BMC Racing Team    0:25:38    
18    Daniel Moreno Fernandez (Spa) Movistar Team    0:31:12    
19    Romain Bardet (Fra) AG2R La Mondiale    0:39:32    
20    Darwin Atapuma (Col) UAE Team Emirates    0:43:48    
21    Stef Clement (Ned) Team LottoNL-Jumbo    0:50:50    
22    Jack Haig (Aus) Orica-Scott    0:54:21    
23    Sander Armee (Bel) Lotto Soudal    0:58:33    
24    Pello Bilbao (Spa) Astana Pro Team    0:59:00    
25    Adam Yates (GBr) Orica-Scott    1:04:10