Aru accelerated literally under Froome's armpit as the race leader raised his hand to indicate a problem. The attack was short-lived, however, as the group of GC favourites, led by Richie Porte (BMC) sat up and waited for Froome.
Froome admitted that he was more concerned with getting a replacement bike than paying attention to Aru.
"I didn't really see what was happening at the front of that group as I was dropping back to change my bike," he said.
However, Froome indicated he would interrogate Aru further about the incident.
"It'll be interesting to see what Aru has to say about it, I'll certainly ask him about it when I next see him."
Aru insisted that he didn't realise that Froome had a problem.
”I didn't know Froome had had a mechanical. When I found out, I stopped,” Aru told Italian television.
“I didn’t see anything because it all happened just as I was going to attack. I always wanted to try for a win a long way out.
"I hadn’t opened up a big gap. I wanted to attack right at that point, six kilometres from the summit. I didn’t see anything. When we heard over the radio that Froome had a problem, I stopped.”
Froome and Aru also had a coming-together soon after Froome regained the elite group, with Froome appearing to shoulder-barge Aru towards the side of the road.
Orica-Scott rider Simon Yates, who was climbing with the elite group when Aru attacked, was in no doubt that Aru knew what he was doing.
"It was clear. It was a really dirty move," said Yates. "But they can do what they want. It's a bike race I guess.
"It's not something you do," he added.
The move has echoes of Aru's former teammate Vincenzo Nibali attacking Froome as he suffered a mechanical on the stage to La Toussuire in the 2015 Tour de France.
The controversial attack was just one incident in a drama-filled stage that saw overall contenders Richie Porte and Geraint Thomas crash out of the race on slippery descents - just two of 12 riders to retire by the end of the stage. The stage was won by Rigoberto Uran, who took a sprint victory despite only being able to use the 11-tooth cog on his rear cassette.
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