The Slovakian was never a favourite in the elite men's road race, which would torment riders with over 4500m of elevation gain, including seven trips over the eight-kilometre climb to Igls and finishing with the Höttinger Höll, a 2.9km steep ascent before the finish.
Sagan made it over the climb to Igls three times, but four proved to be too many, and with 93km to go he had to let go of the peloton. He rode to the end of the lap then abandoned the race.
"As expected, the 2018 UCI World Championship was a race for climbers," Sagan later wrote on his personal web site. "The circuit in Innsbruck was very hard and didn’t suit riders of my type. However, like in every other race, I gave my best and, more importantly, I wanted to honor the rainbow jersey, the way I have been doing since I first won it three years ago in Richmond. Congratulations to Alejandro Valverde for his victory and for becoming the new World Champion."
Sagan won his first world title in Richmond in 2015, attacking over the steep 23rd street climb before bombing the technical descent and holding off the chasers up the short ascent to the line. He followed that in 2016 with an unexpected sprint victory over Mark Cavendish and Tom Boonen in Doha. In 2017, he out-sprinted Alexander Kristoff and Michael Matthews for the win in Bergen.
Over his three years as World Champion, Sagan has been a prolific champion, winning Gent-Wevelgem, the Tour of Flanders, Paris-Roubaix, seven stages of the Tour de France and the European title, amassing 34 wins in the rainbow bands.
He will now spend the first part of the 2019 season in the colours of the Slovakian national champion and Bora-Hansgrohe, having won his country's road race title in June.
After Alejandro Valverde won the world title, Sagan was on hand to present the gold medal to his successor.