Michal Kwiatkowski (Omega Pharma-QuickStep) claimed the biggest one-day race victory of his career in Strade Bianche, distancing breakaway companion Peter Sagan (Cannondale) on the final climb to the finish with a blistering attack.
Alejandro Valverde (Movistar) rounded out the podium to take third place.
"I didn't expect to drop him," Kwiatkowski said after he crossed the line.
"I knew the final pretty well. As a team we were so good today, we had five riders in the front with 50km to go and we controlled the race. I can't describe how I feel. Winning in Siena is an amazing feeling.
"I didn't have any problems in the winter and was focused on my work. I started late compared to last year but I'm really happy with my condition."
Kwiatkowski and Sagan, clearly the two strongest riders in the race, broke clear with 21km remaining after a dangerous move including Cadel Evans (BMC) and Ian Stannard (Team Sky) was caught inside the final 30 kilometres.
Sagan, who was riding with little team support in the final 50 kilometres, was the first to attack, with Kwiatkowski the only one capable of bridging across to the Cannondale rider.
From there the pair set about building on an advantage that peaked at over one minute over the final three sections of gravel roads ahead of the finish in Siena.
Alejandro Valverde, Fabian Cancellara (Trek Factory Racing), Damiano Cunego (Lampre-Merida) and Roman Kreuziger (Tinkoff-Saxo), who all had no answer when the leading pair broke clear, formed a late chasing move but they were unable to reel back the two leaders.
Approaching the final climb, and with Sagan and Kwiatkowski working well together throughout their break, it was the Slovak champion who lead onto the final ascent with the gradient rising to over 16 percent. However, Sagan, who has been subject to numerous transfer stories in recent weeks, had no answer when the Polish champion unleashed a ferocious attack.
Four-man early escape
Earlier in the race Marco Frapporti (Androni Giocattoli), Marco Canola (Bardiani-CSF), Davide Frattini (UnitedHealthcare) and Andrea Fedi (Yellow Fluo) formed the early break, with the foursome quickly establishing a lead close to 11 minutes.
At the half-way point the lead dropped to just under eight minutes, with the majority of the difficult gravel sections still to come. Filippo Pozzato (Lampre-Merida) was a high-profile retiree, pulling out at the feed zone, but Sagan, Evans, Kwiatkowski and last year's winner Moreno Moser (Cannondale) were still in contention with 70 kilometres remaining.
Kwiatkowski punctured on the sixth section of dirt roads but the Pole was quickly paced back to the peloton just as the favourites began to play their hands.
Team Sky, without Bradley Wiggins, who pulled out on the eve of the event, along with BMC set to work on the front of the peloton but it was on the longest section of gravel - 11.5km in total - where the race began to fracture.
The leaders had an advantage of a little over two minutes, but the break began to splinter as the road ramped up with sections close to 20 percent and would soon be neutralised.
Evans and Valverde went out on the attack, joined by Stannard, Kreuziger and two riders from QuickStep. While the moved spelled danger for an isolated Cancellara and Sagan, the pair were soon back with the leaders at the conclusion of the sector. However, it was now a vastly reduced bunch with less than 40 riders still in contention.
Only Peter Sagan (Cannondale), Franco Pellizotti (Androni Giocattoli), Damiano Cunego and Diego Ulissi (Lampre-Merida), Michal Golas, Michal Kwiatkowski, Wout Poels, Matteo Trentin and Rigoberto Uran (Omega Pharma-QuickStep), Warren Barguil, Tom Dumoulin, Simon Geschke and Georg Preidler (Giant-Shimano), Angel Vicioso (Katusha), Salvatore Puccio and Ian Stannard (Sky), Daniele Bennati, Christopher Juul Jensen, Roman Kreuziger (Tinkoff-Saxo), Fabian Cancellara (Trek Factory Racing), Angelo Pagani (Bardiani-CSF), Alejandro Valverde and Andrei Amador (Movistar) had made the split but with five riders in the front group, QuickStep quickly took control.
After setting the initial pace the Belgian team sent Trentin clear with Stannard, Amador, Evans, Geschke and Vicioso bidding to chase.
As the move peaked at an 18-second advantage, Kreuziger took off. However, the Czech only succeeded in bringing the race back together and providing Sagan and Kwiatkowski with their launch pad to attack.
|1||Michal Kwiatkowski (Pol) Omega Pharma - Quick-Step Cycling Team||5:20:33|
|2||Peter Sagan (Svk) Cannondale||0:00:19|