Aru, the young Sardinian who started the race as deputy to veteran team-mate Michele Scarponi, made his move 3km from the summit of the famous climb, which came at the conclusion of the long 225km stage from Valdengo.
Clenching his fists and bellowing his joy, Aru crossed the line 21 seconds ahead of Colombia's Fabio Duarte, with Movistar's Quintana edging Frenchman Pierre Rolland (Europcar) for third place a further second back.
Another Colombian, the race leader Uran of Omega Pharma-Quick Step, kept his cool to cross the line in fifth place, conceding 20 seconds to compatriot Quintana, who rises to fifth place on the general classification, 2:40 behind Uran.
Australian veteran Cadel Evans (BMC) finished more than a minute down on Aru and now trails Uran by 1:03 in second place, with Polish youngster Rafal Majka - the white jersey - now 1:50 adrift in third after rallying to finish just eight seconds behind Uran at the summit.
Aru's win saw the 23-year-old swap positions with Domenico Pozzovivo (AgeR-La Mondiale) in the overall standings: Aru is fourth at 2:24 with the diminutive Pozzovivo dropping to sixth at 3:04.
A thrilling final climb witnessed countless attacks and some fascinating racing as rider upon rider tried their luck on the mountain most famous for the late Marco Pantani’s epic stage win over Pavel Tonkov in 1998.
With the remnants of an initial 12-man break being swept up one by one, the blue jersey Julian Arredondo (Trek Factory Racing) had an early pop alongside Edoardo Zardini of Bardiani-CSF.
Irishman Philip Deignan (Team Sky) attacked from the main pack to reel in the leaders and open up a 15-second gap on the gentler mid-section of the 19km-long climb.
Meanwhile, a series of digs by Rolland behind whittled down the pack of main contenders, with only Quintana, Uran, Duarte and Aru able to follow.
Evans put in a spirited attempt to attack but couldn't muster the requisite power from the ageing legs that delivered him to the 2011 Tour de France crown. As for Pozzovivo – it was perhaps simply an off-day despite (or even because of) all the expectation.
With Aru pulling clear, Quintana tested his legs inside the last 2km to spark a response from Rolland. Uran and Duarte seemed to hold a summit meeting before the Colombia rider danced clear to leave the pink jersey riding his own pace safe in the knowledge that all his main rivals – bar Quintana – were now behind.
Uran looked to be riding back onto the wheels of the chasing trio before Quintana, the 2013 Tour de France runner-up, put in a last-ditch acceleration inside the closing moments.
By this point, Aru had already secured the biggest win of his career – and a first for Sardinia on the Giro - on one of the most revered mountains in Italian cycling.
TWELVE-MAN BREAK: Maxime Bouet (Ag2R-La Mondiale), Daniele Ratto (Cannondale), Johan Le Bon (FDJ.fr), Andre Fernando Cardoso (Garmin-Sharp), Damiano Cunego (Lampre Merida), Adam Hansen (Lotto Belisol), Simon Geschke (Giant Shimamo), Luca Paolini (Katusha), Fabio Felline (Trek Factory Racing), Rodolfo Torres (Colombia), Jackson Rodriguez (Androni Giocattoli) and Enrico Barbin (Bardiani-CSF) formed early on the flat part of the stage to build up a maximum lead of 10 minutes over the peloton.
Riding his eighth consecutive Grand Tour, Australian Hansen attacked at the start of the Plan di Montecampione and was soon joined by Cardoso and Torres – the trio riding only two minutes clear of the peloton. Felline made a spirited effort to join the three leaders before doing some pace-setting duties for his Trek team-mate Arredondo following his attack from the peloton.
Cardoso was the last of the escapees out ahead when Arredondo bridged the gap with 11km remaining. They were caught by Deignan 2km later before being swept up by the streamlined group of main race favourites.
BIG WINNER OF THE DAY: On top of taking the first major win of his career, Aru jumped to fourth on GC – not bad considering his role at this Giro started very much in service of his aged Astana team-mate Michele Scarponi. Quintana can be happy with his day’s work, having eaten a little into Uran’s overall lead ahead of the final rest day on Monday.
BIG LOSERS OF THE DAY: Veteran Italian Ivan Basso had another bad day in the saddle, but Evans managed to contain his losses. Both Pozzovivo and Wilco Kelderman lost valuable time and a couple of places each on GC.
KEY MOMENT: Aru’s first attack came with 3km remaining. Only Uran could follow – and the pair rode clear in pursuit of Rolland, Deignan and Duarte. Quintana hesitated before joining the game – but no one else had it in them to join the battle. Once Uran and Aru had joined the leaders, the Italian then put in an attack with 2km remaining – and this time there was no response.
TALKING POINT: Is it already a case of daily damage limitation for Rigoberto Uran? As long as he can finish within 20-odd seconds of Quintana each day, then he should be able to stay in pink – especially if his other rivals keep slipping back on the decisive climbs.
COMING UP: The riders take a well-earned rest day on Monday ahead of the final six stages of the race.
- Sports & Recreation
- Fabio Duarte
- Pierre Rolland
- Michele Scarponi
- Domenico Pozzovivo
- Cadel Evans
- Rigoberto Uran