American quad-jumping sensation Nathan Chen surged to the lead after the men's short programme as Japan's Shoma Uno struggled in fifth in the world figure skating championships on Thursday.
Olympic champion Yuzuru Hanyu of Japan has skipped the post-Games worlds with an ankle injury along with former two-time winner Javier Fernandez of Spain, who took Olympic bronze in Pyeongchang.
Chen -- the ISU Grand Prix final champion -- made up for his nervy short progamme in Pyeongchang which resulted in his fifth-place finish in South Korea.
Despite a wobbly landing on his triple axel in Milan the 18-year-old nailed all his elements in his routine to Benjamin Clementine's 'Nemesis' to earn 101.94 points.
"It wasn't a perfect short programme but I'll take it," said the skater from Salt Lake City.
"It was definitely pretty great to be able to come back here and skate like I did," he added of his disappointing Olympics.
"I'm using what I learned in the Olympics here."
Chen became the first figure skater to land six quads as he set an Olympic record in the free skate four weeks ago and he vowed "to try five quads" in Saturday's free skating final.
But he added: "Ideally to stake clean."
In Hanyu's absence 20-year-old Uno was seen as favourite to move up from his silver medal last year after finishing runner-up at the Olympics.
But errors in his routine to Vivaldi's Four Seasons left him trailing 7.68 points behind Chen.
Russian Mikhail Kolyada was second best with 100.08 points followed by last year's world junior champion Vincent Zhou of the United States (96.78) followed by China's Jin Boyang (95.85) and Uno (94.26).
The competition continues on Thursday with the pairs free skating final where Olympic champions Aljona Savchenko and Bruno Massot of Germany are bidding for their first world title together.
Savchenko -- who won five world crowns with now-retired Robin Szolkowy -- will be bidding to match Norwegian legend Sonja Henie for the female record of 11 world championships medals.