Long hailed as cycling's next big thing, Sagan hid in the bunch for most of the punishing 261.4km race, then lived up to his promise as he pulled away and held on for a three-second win over Australian Michael Matthews.
As he crossed the finish line, Sagan lifted his hands in triumph, got off his bike and tossed it up the road.
Lithuania's Ramunas Navardauskas was third.
"I am very happy, I was fighting always in the Tour de France and in the summer classics I was in the front but not the best," the playful Sagan told reporters. "I am very happy for one big victory like this.
"I cannot believe this. The rainbow jersey is best for me I think. I can stop my career now...I am joking."
A rider with decent sprinting qualities added to a capacity to master short and brutal ascents, the Richmond course with its sharp punchy climbs, including two up cobblestones, was tailor made for the 25-year-old.
For much of the race, Sagan was the invisible man, patiently biding his time hidden in the peloton until seizing his chance with three kilometres to go when he decided to make a solo break.
Shrugging off injuries he sustained when he crashed out of the Vuelta a Espana last month after colliding with a race motorbike, Sagan timed his attack to perfection as he surged to the front of the bunch up the Libby Hill cobblestones.
CHARGING PACK
The flamboyant Slovakian then made the bold decision to go it alone, powering up the final cobblestone pitch and leaving just enough in the tank to reach the line ahead of the charging pack in a time of 6 hours, 14 minutes and 37 seconds.
"From the last climb, it was still a long way until the finish," said Sagan. "The climb was very hard, the climb was very short but the last 800 metres was very tough.
"If you go alone from that moment until the finish, it was far away and when you see the group behind you know everybody will go full gas to hunt you.
"But I said I have to go because if I go back and wait for the sprint, I can do second, third, four, fifth, but when I decided to go alone, it was the best moment."
It was a popular and long overdue victory for the Slovakian showman.
Sagan has managed eight top-10s in the Monument Classics, but had never won despite being the pre-race favourite several times.
He has won four successive Tour de France green jerseys and as many stage wins, yet this year he finished second on five occasions.
This time, it was left to Matthews to deal with the sting of finishing runner-up.
"I was obviously disappointed coming in as a favourite and coming up second," said Matthews. "I did a good sprint, did a good race but unfortunately we came up one short."
(Editing by Mark Lamport-Stokes)
Share
