On the mountain-top finish, Yates showed his first signs of weakness all tour, being dropped by his main rivals and losing 28 seconds to Tom Dumoulin, who now trails him by the same figure in the overall standings.
It was a day of great promise for Dumoulin, though less so for New Zealand's George Bennett, who will need to make his inroads in the following two mountain stages after he dropped out of the top 10 this morning.
On a stage which saw the breakaway finally allowed to compete for glory, talented German all-rounder Maximilian Schachmann was the strongest, taking out the victory as the general classification riders had their own battle, 10 minutes down the road.
It was a battle which Bennett struggled with, being surpassed by Patrick Konrad in the overall standings after losing 13 seconds to the Austrian on the final climb.
Just the solitary second separates the pair now, with Bennett sitting in 11th place, seven minutes and six seconds behind Yates. More importantly, he falls to 67 seconds behind ninth place, after failing to make back ground on any of his fellow contenders on the closing 13 kilometre climb.
It wasn't for a lack of trying - with less than four kilometres remaining, Bennett attacked from the group of 15 remaining riders. He was aiming to make time on the riders near him on GC - the likes of Konrad and Pello Bilbao - but that particular duo were quickly on his wheel.
As they ground out a slight advantage on the chasing pack, all hell broke loose, with Dumoulin launching a vicious attack, followed by Yates and Domenico Pozzovivo. That negated the work Bennett had put in, and while the group was all back together with 1.5 kilometres to go, the attacks didn't stop.
Chris Froome's endeavour was the pivotal one, causing the big players (and chaos) to follow. As Bennett drifted off the back of the group, he was shockingly joined by Yates, who couldn't hold the wheel of the favourites in the final kilometre.
While he didn't suffer the strangest fate - Wout Poels took a totally wrong turn in the final bends - Yates' suffering puts new life into a race which looked as if the Brit was set to ease to glory.
On an earlier stage, the finals climb's average gradient of 7% wouldn't have been a problem, but with all the other contenders launching attacks for his jersey, Yates cracked. Now, his slender 28 second lead over Dumoulin is eminently seizable, especially with a monster of a stage coming tomorrow.
It's difficult to even describe how difficult stage 19 will be, so here's a picture.
Look at those climbs! That, my friends, is two absolutely brutal tests, and anyone not at their best will be truly found out and could lose massive chunks of time.
It should suit Bennett more than some of his rivals - Konrad, Bilbao and Rohan Dennis in particular - and this is his big chance to lock in a top 10 finish. However, due to a mixture of horrendous luck and poor timing with his attacks, week three of the Giro hasn't seen Bennett display his best form.
Make no mistake, tomorrow he'll need it.
- Niall Anderson
