Reigning champion Nathan Chen skated his best score of the season to take the lead in the short program at the World Championships of Figure Skating in Saitama, as an error on his opening jump left double Olympic champion Yuzuru Hanyu in third.
Jason Brown of the United States delivered a sensational, quad-less clean skate to earn his season-best score of 96.81 and claim a surprise second place.
Hanyu, coming back to competition for the first time since suffering an ankle injury at Rostelecom Cup in November and the subject of huge adoration from the home crowd, popped his opening quad salchow to a double after struggling with the jump in the warm-up.
Chen, the last skater in the final group, skated clean to score 107.40, and take a comfortable lead ahead of Saturday's free skate.
I'm going to use what I did today to build the confidence for Saturday. - Nathan Chen
The 19-year-old American insisted entering the competition as reigning champion had not altered his approach.
"I like to tell myself that everything I've done in the past, whether good or bad, stays in the past," he said. "And so coming into these Worlds was no different than coming into any other Worlds, despite having the success that I had at last Worlds.
"I'm happy with the way I performed and I'm going to use what I did today to build the confidence for Saturday."
Nathan Chen: "This has been my favourite season so far"
Nathan Chen: "This has been my favourite season so far"The reigning World champion is pleased of his performance after leading the Men's Short Program at the Figure Skating World Championships in Saitama, Japan.
Speaking to the media after his skate, which scored 94.87, 24-year-old Hanyu admitted nerves had played a part.
I'm just really feeling a little nervous for my skating. - Yuzuru Hanyu
"I'm very disappointed with my short program, I made a very big mistake," he said. "I think I should have had more confidence and assumed a feeling of being more like the champion and gone in [to the jump] appropriately.
"I'm just really feeling a little nervous for my skating. I'm trying to get more confidence for my long program.
"I feel really frustrated by this performance."
Hanyu now has a fight on his hands in the free skate to win a third world title after Chen opened up a 12-point gap.
Yuzuru Hanyu: "I should have had more confidence"
Yuzuru Hanyu: "I should have had more confidence"The double Olympic champion says he was 'disappointed' after his third place in the Short Program at the Figure Skating World Championships.
A crash for Shoma Uno
Brown, a rink-mate of Hanyu's after moving to train under coach Brian Orser in Toronto this season, was delighted to put down a personal best.
"I've been working so, so hard at home and putting in hours and the time and working so hard to work on all the changes that we've been making throughout the season," said 24-year-old Brown.
"So to be at the World Championships and get a personal best and put out that performance, I'm just super, super pleased."
Jason Brown: "Yuzu has pushed me every day to be a better skater"
Jason Brown: "Yuzu has pushed me every day to be a better skater"The Sochi 2014 bronze medallist thanks double Olympic champion Hanyu after his second place in the Men's Short Program.
Shoma Uno, another home favourite for Japan, fell on his opening quad flip and made his planned triple toeloop a double in the combination to place sixth. Vincent Zhou, also of the United States, and Italian Matteo Rizzo placed fourth and fifth respectively.
If you want to re-live what happened on Thursday at the ISU Figure Skating World Championships check out our live blog.