Unheralded Kazakhstani Maxim Iglinskiy stunned a host of favourites to claim the biggest win of his career at a rain-hit Liege-Bastogne-Liege here on Sunday.
Italian Vincenzo Nibali, who looked to have secured his maiden victory in cycling's oldest one-day classic until Iglinskiy overtook him on the 11th and last climb of the 257.5 km epic, finished runner-up at 21sec.
It was Astana's second major win inside a week, after Enrico Gasparotto's victory at the Amstel Gold Race in the Netherlands.
Italian Gasparotto completed the podium after beating Frenchman Thomas Voeckler (Europcar) and Ireland's Dan Martin (Garmin) to third place.
Astana team manager Guido Bontempi admitted Gasparotto had been their main hope for victory in the third of the Ardennes Classics races.
But Iglinskiy forged his own winning chance when he dropped one race favourite, Spaniard Joaquim Rodriguez, on the climb to Saint Nicolas before chasing down a tiring Nibali and overtaking him with 1.1 km to race.
"It's the biggest win of my career," said the 31-year-old Kazakh, who revealed he had been spurned on to try his luck by former two-time winner, compatriot Alexandre Vinokourov.
"Alexandre called me this morning and told me I could win this race, but that I had to try and get into a breakaway."
Bontempi admitted: "It's a big surprise for us. We came here looking for a good result and now we've won two out of the past three races, it's amazing."
Defending champion Philippe Gilbert of BMC was among several big contenders who failed to shine on a day marked by intermittent rain showers and cold temperatures.
The Belgian, who had signalled his ambitions by finishing third behind Katusha team leader Rodriguez at the Fleche-Wallonne semi-classic in midweek, was left trailing when Iglinskiy and Rodriguez attacked in a bid to reel in Nibali.
He eventually finished 16th at 1min 27sec behind.
Former two-time winner Alejandro Valverde was at the back of the peloton during some of the key latter stages before suffering a mechanical problem which later prompted him to borrow a teammate's bike.
To add to the Spaniard's woes, he was later declassified along with three of his teammates for going off course.
The Schleck brothers Frank and Andy, who finished second and third respectively behind Gilbert in 2011, also flattered to deceive.
Frank was by far the better of the pair, but the Luxemburger failed to contend the finale after being dropped on the Redoute climb, the third last in the race where the summit was 34.5 km from the finish.
Schleck finished among a 20-strong group just behind Gilbert at 2:11.
Former Tour of Spain champion Nibali appeared to victory within his grasp when he left Gilbert and several other fellow favourites behind at the top of La Roche aux Faucons climb, with 19.5 km to race.
But despite building a lead of over 20secs on the chasers, his legs eventually gave way on the last climb to the finish in Ans.
"It's a pity. I launched a pretty good attack," said the Liquigas rider.
"I just ran out of juice in the final. There was a lot of wind on the climb to Saint Nicolas, and I spent a lot of energy there."
He added: "Iglinskiy is a very good rider but I would have preferred to have been beaten by Gilbert."
Gilbert, who last year won all three Ardennes Classics, was quick to concede defeat.
"I was feeling good until the top of the Roche aux Faucons, but after Nibali attacked I tried to follow and quickly realised I didn't have the legs," said the Belgian.
First held in 1892, Liege-Bastogne-Liege is known as the Doyenne because it is the oldest existing one-day race on the calendar.