The Swiss quadruple time trial World Champion withdrew from the Vuelta a España last week with a stomach illness, and has now decided to end his 2015 season.
His Vuelta withdrawal was the latest 2015 set-back after suffering from two fractured vertebrae in the E3 Harelbeke and crashing out of the Tour de France while in the race lead, again fracturing two vertebrae.
Cancellara was hoping to contest the men's road race - a title that is missing from his impressive palmares that includes eight Tour de France stages, three editions of Paris-Roubaix and three Tour of Flanders victories, among many others.
“Physically I could probably go on and race the World Championships," said Cancellara in a Trek team statement. "But it’s the mind that controls the body, and I don’t have the will to go through the whole come-back thing once more after the rollercoaster that this season has been.
"It's a matter of focus. Dealing with a serious injury during the course of one season is not easy, and I have had to do it twice already this year. It’s mentally very challenging and it drains your energy. I don't have batteries anymore for a third come-back in one season."
As well as racing for his home nation of Switzerland, Cancellara was scheduled to ride in the team time trial for Trek Factory Racing.
"I’m sad not to be racing the Worlds, of course. The TTT is an important race for our team and everybody knows how much I love racing for Switzerland. I'm sorry for the TFR boys," he said.
"The Worlds next year don't suit me very well, I'm not a sprinter. This could have been my last chance, but then again, the way this season is going for me, not really."
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