A few seconds after Romain Bardet (AG2R La Mondiale) had put in a punchy but short-lived acceleration, the Colombian attacked four kilometres from the summit, briefly dropping Chris Froome (Team Sky) while Alberto Contador (Trek-Segafredo) and Vincenzo Nibali (Bahrain-Merida) bridged across.
Chaves' move effectively set fire to the GC battle on what had been a relatively calm assault on La Pandera, but he paid a price for it. As Contador observed later, one key lesson he had learned on the 12-kilometre ascent was that "everybody is getting close to their limit, we're deep into the second week now" and Chaves, having raised the temperature of the stage with his attack, then suffered as a result.
Froome clawed his way back to the little attack group relatively quickly, and with Calar Alto stage winner Miguel Angel Lopez (Astana) in his wake. When Lopez promptly blasted away, Chaves could not hold the change in pace. He crossed the line 26 seconds down and has dropped from third overall to fifth, behind Wilco Kelderman (Team Sunweb) and Ilnur Zakarin (Katusha-Alpecin).
"It was a hard day, with teams like Astana, Trek and Bahrain making the pace from a very long way out," Chaves said afterwards. "Everyone was suffering.
"I'd watched the video of the ascent this morning [from a previous Vuelta] and I knew it would be hard going. I was very aggressive on the hardest part at four kilometres, but in the end, I paid for that, so I just came over the line."
As Contador had observed, too, Chaves confirmed there was no real sense among the GC contenders that Froome had had a bad day, just because he had briefly fallen behind. "He's a super strong guy and he knows how to pace himself," Chaves pointed out, before adding that "he finished in the same time as the other guys."
Chaves predicted even more fireworks for Sunday's stage, which he described as "short and hard, the kind the public like. Everyone's going to go super-deep, because the next day is a rest day."