Published 16/10/2016 at 08:02 GMT | Updated 16/10/2016 at 20:27 GMT
The irrepressible Sagan burst down the right-hand side of the closing straight before powering clear of his rivals – leaving a frustrated Cavendish, the 2011 world champion, in his wake for second place ahead of Belgian veteran Tom Boonen.
Mark Cavendish was edged into second place in a sprint finish at the Road World Championships
Image credit: PA Sport
Australia's Michael Matthews took fourth place and Italian Giacomo Nizzolo was fifth as a select 25-man group contested the showpiece finale of the 2016 World Championships in Doha.
If Sagan stole the show by sprinting to back-to-back world titles it was Boonen’s Belgium team who took the 256.5km race by the scruff of its neck after the peloton blew apart in crosswinds during the out-and-back loop in the desert of the Arabian Peninsula.
With a seven-man break riding some 10 minutes clear as the peloton took a sharp 90-degree turn on the northern-most point of the outward loop, the peloton fragmented into numerous echelons in the crosswinds near the town of Abu Yazoul – still with some 175km remaining.
Belgian placed six men in a leading group of around 30 riders – including Olympic champion Greg van Avermaet and 2005 world champion Boonen – and had two men expertly marshalling a disgruntled chasing group that included German trio Andre Greipel, Marcel Kittel and John Degenkolb.
A gap of 30 seconds had stretched to over a minute as the main group swallowed up the initial escapees and entered Doha ahead of seven 15.2km laps of the Pearl.
Also frustrated by the multiple splits were Frenchman Nacer Bouhanni and Dutchman Dylen Groenewegen – while Australian youngster Caleb Ewan was first of the big names to withdraw after riding into Doha in a distant gruppetto.
The leading group was a roll call of top sprinters and classic riders: joining the reigning world champion and two former world champions were the fancied Norwegian duo Alexander Kristoff and Edvald Boasson Hagen, Italian fast men Elia Viviani and Nizzolo, and Dutch powerhouse Niki Terpstra.
Cyclists compete in the men's elite road race event as part of the 2016 UCI Road World Championships on October 16, 2016, in the Qatari capital Doha
Image credit: AFP
But it was the Belgians who held the upper hand as both Boonen and van Avermaet were able to take a back seat while Jurgen Roelandts, Jasper Stuyven, Oliver Naisen and Jens Keukeleire controlled the tempo and led the pack over the finish line at the conclusion of each lap.
Behind, frustrations rose with Degenkolb lashing out at Belgium’s Jens Debusschere – spraying his colleague with a water bottle before gesticulating wildly – after every attempt Germany made to close the gap was gamely thwarted by Debusschere and his compatriot, Iljo Keisse.
With the gap growing to over three minutes with two laps remaining, Degenkolb and Kittel both threw in the towel with apparent heat exhaustion leaving veteran Greipel to fly the flag for Germany on a disappointing day for the much touted nation.
Doha 2016 UCI World Championships men's road race
Image credit: Eurosport
With two laps remaining it was certain that one of the leading group of 25 rider would contest the win. But Boonen and van Avermaet were not the only two of the contenders who were able to keep their powder dry.
Cavendish, whose British team-mate Ian Stannard had been responsible for forcing the initial split in the crosswinds, was able to lean on compatriot Adam Blythe, while Matthews kept himself invisible behind the sturdy frame of fellow Australian Mat Hayman, the surprise Paris-Roubaix winner back in April.
Sagan, too, could rely on fellow Slovak Michal Kolar after benefitting from some superb earlier work by his brother, Juraj – agonisingly distanced while fetching water bottles for the world champion.
Italy had multiple cards to play with Olympic omnium gold medallist Viviani riding alongside Nizzolo, Jacopo Guarnieri and the veteran Daniele Bennati.
Cyclists compete in the men's elite road race event as part of the 2016 UCI Road World Championships on October 16, 2016, in the Qatari capital Doha.
Image credit: AFP
But it was a Dutchman who eventually threw a cat amongst the pigeons: not Terpstra, as expected, but Tom Leezer, who darted clear with 2.5km remaining to open up a commanding lead in the closing moments. The 30-year-old still held a gap going under the red kite – but Leezer was swept up just 300 metres from the finish after the expected sprint opened up.
As Sagan powered down the right, Cavendish found his path blocked momentarily by Matthews and was forced to check his speed and take a different line. This – and Nizzolo not closing the door on Sagan – made all the difference.
Sagan, 26, surged clear to win by a bike length while Cavendish was forced to settle for second place ahead of Boonen, who was unable to turn Belgium’s numerical advantage into a gold medal. (Van Avermaet, the second best-placed Belgian, could only finish tenth ahead of Tepstra and French wildcard William Bonnet.)
Instead, the rainbow stripes will adorn the jersey of Peter Sagan for a second successive year – just rewards for the rider who in a stellar 2016 topped the UCI World Tour standings, who won the European championships and the Tour of Flanders, and who secured a fifth successive green jersey during July’s Tour de France.
Slovakia's Peter Sagan celebrates after winning the men's elite road race event as part of the 2016 UCI Road World Championships on October 16, 2016, in the Qatari capital Doha
Image credit: AFP
"I don't believe it – I'm still in shock," said Sagan after becoming the first rider since Paolo Bettini in 2007 to secure successive world titles.
"I'm very happy because I was the last one to close the gap in the crosswinds. It's unbelievable. Thank you to everybody from Slovakia and to my fans, family and friends. I felt a lot of energy today."
Peter Sagan: I can’t believe it, I am in shock
Sagan was also full of praise for his two Slovak team-mates – brother Juraj and fellow Tinkoff rider Kolar – both of whom played a vital role in him defending his title with such aplomb.
Norwegian duo Boasson Hagen and Kristoff settled for sixth and seventh place in Qatar – but will hope to put up a stronger fight when the UCI World Championships take place in their native Bergen in 2017.