Simon Yates (Mitchelton-Scott) showed his first signs of weakness in the 2018 Giro d'Italia as he lost half of his advantage at the top of the general classification on stage 18's summit finish, which was won by Maximilian Schachmann from the day's early break.
Yates had looked comfortable for most of the climb to Prato Nervoso but was put in trouble after Chris Froome (Team Sky) countered a move by Tom Dumoulin (Team Sunweb) which the Dutchman then followed.
Froome, Dumoulin and Domenico Pozzovivo (Bahrain-Merida) then conspired to drive the pace to the line through the final kilometre while Yates leaned on team-mate Mikel Nieve to limit the damage.
In the end Yates crossed the line 28 seconds behind his main GC rivals, meaning that his lead at the top of GC is now down to 28 seconds with two big mountain stages coming on Friday and Saturday.
Meanwhile the stage win was contested by the breakaway after the day's early move was allowed a long leash to take a 15 minute lead onto the final climb.
The 12-strong group was steadily whittled down on the steady ramps to Prato Nevoso with three riders, Schachmann, Mattia Cattaneo (Androni-Sidermec), and Ruben Plaza (Israel Cycling Academy), entering the final 500m together.
Schachmann had looked the strongest up the climb as he followed Cattaneo's repeated attacks, launching his bid for glory with 400m to go and crossing the line with time to spare for his first Grand Tour stage win.
How it happened
The first of three mountain stages that will decide the Giro d'Italia, stage 18 featured an almost entirely flat first 170km on the way to a summit finish in Prato Nevoso. The profile didn't looking promising for the breakaway, but that didn't stop 12 riders getting in the early move.
In the day's break were Michael Mørkøv and Maximilian Schachmann (Quick-Step Floors), Davide Ballerini and Mattia Cattaneo (Androni-Sidermec), Christoph Pfingsten (Bora-Hansgrohe), Ruben Plaza (Israel Cycling Academy), Viacheslav Kuznetsov (Katusha-Alpecin), Jos van Emden and Boy van Poppel (Trek-Segafredo), Marco Marcato (UAE Team Emirates), and Giuseppe Fonzi and Alex Turrin (Wilier Triestina-Selle Italia).
Those riders took a little while to get away from the bunch, being held at less than 30 seconds for the first 20km, before the pace eased in the group behind and they were able to open a more substantial lead which quickly rose to 13 minutes.
Mitchelton-Scott patrolled the front of the bunch but, with two tough days coming up on Friday and Saturday, showed little inclination to want to chase the break which kept its lead at around 13 to 14 minutes for much of the day.
The only moment of action for the rest of the stage came as Giuseppe Fonzi opened his legs to take the fourth category climb at Novello, picking up enough points to move himself into 43rd place in the mountains classification.
However aside from that brief flurry of action this stage was all about the summit finish to Prato Nevoso, and by the time the break approached the climb their lead was up to a massive 15 minutes.
With 18.8km to go Boy Van Poppel, probably the weakest climber in the move, was the first to flinch in the break, attacking solo as the road started to edge upwards on a false flat approach to the climb up to the ski resort.
Van Poppel quickly established a lead of 30 seconds over his erstwhile breakaway companions, but that lead quickly dropped away as the climb started in anger with Mørkøv and Ballerini leading the group.
The next rider to make a move was Marcato whose acceleration with 9.5km to go slimmed the group down, before Plaza put in a more concerted efforts that cut things down to just seven riders.
However Plaza looked vulnerable after his move and was quickly countered by Cattaneo before Schachmann put in another move that only the Italian could follow at first.
Those two riders hovered agonisingly close to Plaza and Pfingsten, but Schachmann's accelerations made look like that it would be a two horse race to the finish.
Heading into the final 1.5km and Cattaneo put in two big move to try a dispatch with Schachmann, but the Quick-Step Floors rider was equal to him and looked the strongest and smoothest heading under the flamme rouge.
However from nowhere Plaza regained contact with a kilometre to go, but had no answer to Schachmann's move with 400m to go as the 24-year-old sprinted away to take his first Grand Tour win.
Back in the peloton there were a few nerves in the bunch as Mitchelton-Scott found themselves challenged at the front by Team Sky, Groupama-FDJ, LottoNL-Jumbo and Astana, all looking to make sure that their various team leaders were in a good position at the base of the climb.
The first half of the climb was controlled by Mitchelton-Scott, but it was Movistar who raised the pace with 6.5km to go to string the group out with Richard Carapaz's rival for the white jersey, Miguel Angel Lopez, appearing to be in trouble at the back.
One man who Lopez wouldn't have to help was Astana team-mate Pello Bilbao who attacked the peloton, being joined out front by Wout Poels (Team Sky) and Ben O' Connor (Dimension Data).
While O'Connor and Bilbao were dropped by Poels, Lopez made his way back up to the front of the pink jersey group, before launching a counter-attack against a move by Carapaz and ride his way up to Poels and go straight past the Dutchman.
Sebastien Reichenbach (Groupama-FDJ) led the chase on behalf of Thibaut Pinot with Simon Yates looking comfortable in third wheel, as a few moves from the likes of George Bennett (LottoNL-Jumbo) and Patrick Konrad (Bora-Hansgrohe) flew off the front in the pursuit of the minor GC places.
But the battle for the top of the GC really picked up as Tom Dumoulin launched a move with 1.5km to go, an acceleration which was followed by all of the top GC riders, before Chris Froome launched an acceleration of his own.
Unsurprisingly it was Domenico Pozzovivo who followed with Dumoulin in the wheel, and for the first time in the Giro d'Italia there was the chink in the armour for Yates as he was unable to follow.
Froome quickly joined up with Poels who set the pace, but Yates was in real trouble as he was even dropped by Carapaz, Bilbao and Konrad within the final kilometre.
There was a brief moment of drama as Poels nearly went the wrong way at the final corner, but Dumoulin drove Froome and Pozzovivo all the way to the line as Yates was paced by Mikel Nieve behind.
In the end Yates crossed the line 28 seconds down on Dumoulin, Pozzovivo, and Froome, meaning that his lead over Dumoulin was halved to just 28 seconds with two big mountain stages to come.
Giro d'Italia 2018, stage 18: Abbiategrasso to Prato Nevoso, 196km
1. Maximilian Schachmann (Ger) Quick-Step Floors, in 4-55-42
2. Ruben Plaza (Esp) Israel Cycling Academy, at 10 secs
3. Mattia Cattaneo (Ita) Androni Giocattoli-Sidermec, at 16 secs
4. Christoph Pfingsten (Ger) Bora-Hansgrohe, at 1-10
5. Marco Marcato (Ita) UAE Team Emirates, at 1-26
6. Michael Mørkøv (Den) Quick-Step Floors, at 1-36
7. Viacheslav Kuznetsov (Rus) Katusha-Alpecin, at 1-32
8. Jos van Emden (Ned) LottoNL-Jumbo, at 3-22
9. Alex Turrin (Ita) Wilier Triestina-Selle Italia, at 3-29
10. Davide Ballerini (Ita) Androni Giocattoli-Sidermec, at 5-09
General classification after stage 18
1 Simon Yates (GBr) Mitchelton-Scott, in 75-06-24
2 Tom Dumoulin (Ned) Team Sunweb, at 28 secs
3 Domenico Pozzovivo (Ita) Bahrain-Merida, at 2-43
4 Chris Froome (GBr) Team Sky, at 3-22
5 Thibaut Pinot (Fra) Groupama-FDJ, at 4-24
6 Miguel Angel Lopez (Col) Astana, at 4-54
7 Rohan Dennis (Aus) BMC Racing, at 5-09
8 Pello Bilbao (Spa) Astana, at 5-54
9 Richard Carapaz (Ecu) Movistar, at 5-59
10 Patrick Konrad (Aut) Bora-Hansgrohe, at 7-05
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