Nairo Quintana took over half a minute off Chris Froome's general classification lead but has possibly left it too late with just one day of racing left, as defending Tour de France champion Vincenzo Nibali won for the first time this year on stage 19.
The majority of the arduous 138-kilometre ride from Saint-Jean-de-Maurienne to La Toussuire-les-Sybelles was all uphill, with the field tasked with 61.5km of climbing.
Nibali - who won by almost eight minutes in 2014 - has had a relatively quiet Tour, but broke clear of the yellow jersey group after Froome (Team Sky) suffered a brief mechanical problem and it proved a good decision as the Astana man moved up to fourth in the general classification.
Quintana managed to rid himself of Froome in the closing stages and his move means he trails by two minutes and 38 seconds ahead of a mouth-watering penultimate stage that includes a gruelling trek up l'Alpe-d'Huez.
The difficulty of the stage was highlighted on the first climb of the day, as Froome's team-mates struggled to cope with attacks from Alberto Contador (Tinkoff-Saxo) and Alejandro Valverde (Movistar).
Sky were reunited when the roads flattened, but a treacherous climb up the Col du Glandon proved too much for the likes of Richie Porte and Geraint Thomas - who dropped out of the top 10 in the general classification.
There was a moment of worry for Froome when he appeared to get a stone stuck in his brake and had to amend the problem. He quickly caught the yellow jersey group and appeared to exchange angry words with Valverde.
Quintana made his move on Froome with 5km, and the yellow jersey holder reacted to drop Contador and Valverde.
The Colombian's attack proved just too late to catch Nibali, but Froome was not able to keep pace with Quintana who chipped 32 seconds off the lead with one proper day of racing remaining.
The stage wasn't without its fair share of controversy, with Froome accusing Nibali of acting in an unsportsmanlike manner in his stage 19 win.
Defending champion Nibali (Astana) made a break for the lead after spotting that Froome had encountered a problem, with the Team Sky man getting a stone stuck in his rear brake.
"A bit of tar or a small stone had locked itself between my brake calliper and back wheel so I had to stop and take the wheel backwards to get the stone out," Froome said.
"Unfortunately that was the moment that Nibali decided to make his move. He did see what he was doing, I'm pretty sure he looked around, saw I was in trouble and attacked.
"In my opinion you don't do that to the race leader, it's not sportsmanlike."
Nibali defending his actions after his victory, saying that he felt it was within his rights to attack Froome at that point in time.
"I haven't seen Froome had a problem. I looked behind because I was looking for [team-mate Tanel] Kangert. We didn't receive any such info via radio.
"It's been a difficult Tour de France for me. You have seen it. I had trouble in the first week. I did better in the second week. I feel better this week.