Nibali (Astana) rode away from the lead group 3km from the top of the Col de la Croix de Fer. He held his advantage down the descent and completed the best stage of his 2015 Tour campaign with a solo ride up La Toussuire.
The 2014 Tour champion finished 44 seconds in front of second placed Nairo Quintana (Movistar) and 1min 14sec in front of an angry Froome (Sky).
"I suddenly felt like my back wheel locked up, a bit of tar or a small stone had locked itself between my brake calliper and back wheel,” said Froome after the stage, explaining why he was forced to pull over to the side of the road.
“I had to stop and take the wheel backwards to get the stone out. 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. He had the whole climb to attack and he waited until I had a mechanical. You certainly wouldn’t find me attacking a race leader like that.”
While he was calmer in front of the media, Froome reportedly had much stronger words to say to Nibali at the finish line.
“I won't say the words he used because they're too harsh and it's not nice to say them,” Nibali, who stood by his decision to attack when he did, said.
“He was very angry but I don't know what his problem was. Lots of things happen in a race.
“Before judging, you need to think and use your brain. We're all nervous after the stage but he (verbally) attacked me. But I didn't reply, I didn't say anything,” said Nibali.
The stage winner claimed that when he looked behind before the attack, it wasn’t Froome he was looking at, it was his team-mate, Tanel Kangert. Attacking on the Col de la Croix de Fer had always been part of their race plan.
The unwritten rules of the race state that one rider should never attack another when they’re down, if it is through no fault of their own, which has tainted Nibali’s attack as a dirty move.
“Lots of things have happened to me too, but that's cycling,” said Nibali, defending his actions.
The Italian stated that he didn’t hear any information on the situation through the race radio, only time gaps confirming the advantage he had gained over his rivals: 40 seconds at the top of the Col de la Croix de Fer and two minutes at the bottom.
“When Contador crashed on the descent (of the Col d’Allos) we didn't know until three or four kilometres after. It happens a lot of times in races. I can remember when I crashed at the 2010 Giro d'Italia, at Montalcino. There was the incident when Andy Schleck was attacked by Contador at the Tour the other year. There are no rules.”
Riding from seventh position in the general classification, it was highly unlikely that Nibali was going to out-ride Froome by more than eight minutes, the time needed to overtake the Briton on the general classification. But this incident is not the first time tensions have been high between the 2013 and 2014 winners of the Tour.
Nibali wrongly accused Froome of causing him to crash moments before the finish line on Stage 6, the crash that saw Tony Martin (Etixx-QuickStep) leave the Tour with a broken collarbone while wearing the yellow jersey. Froome marched to the Astana bus after the stage to rectify the situation. Nibali stood down after video footage confirmed he was in the wrong.